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Saprolegnia, Achlya, Pythiopsis, Dictyuchus, Aplanes. Motile zoospores a yeast, and even bring about alcoholic fermentation in a saccharine which escape from the zoosporangium are present except in A planes. solution. The sexual reproduction shows all transitions between forms which The segments of the hyphae in this group usually contain several are normally sexual, like the Peronosporaceae, to forms in which nuclei. At the time of sporangial formation the protoplasm with no antheridium is developed and the oospheres develop partheno numerous nuclei streams into the swollen end of the sporangiophore genetically. The oogonia, unlike the Peronosporaccae, contain more and there becomes cut off by a cell-wall to form the sporangium. than one oosphere. Klebs has shown that the development of The protoplasm then becomes cut up by a series of clefts into a zoosporangia or of oogonia and pollinodia respectively in Saprolegnia number of smaller and smaller pieces which are unicellular in is dependent on the external conditionsso long as a continued Pilobolus, multicellular in Sporodinia. These then become surstream of suitable food-material is ensured the mycelium grows on rounded by a cell-wall and form the spores. This mode of sporewithout forming reproductive organs, but directly the supplies of formation is totally different from that in the ascus; hence one of nitrogenous and carbonaceous food fall below a certain degree of the difficulties of the acceptance of Brefeld's view of the homology concentration sporangia are developed. Further reduction of the of ascus and sporangium. The cytology of zygospore-formation is supplies of food effects the formation of oogonia. This explains the known detail; sequence of events in the case of a Saprolegnia-mycelium radiating the so-called gametes from a dead fly in water. Those parts nearest the fly and best which fuse are multisupplied develop barren hyphae only; in a zone at the periphery, nucleate and are no doubt where the products of putrefaction dissolved in the water form a of the nature of gamedilute but easily accessible supply, the zoosporangia are developed tangia. The fate of these in abundance; oogonia, however, are only formed in the depths of nuclei is doubtful. prob. this radiating mycelium, where the supplies of available food ably they fuse in pairs materials are least abundant.

(fig. 6). Chytridincae.-These parasitic and minute, chiefly aquatic, forms Blakeslee has lately may be looked upon as degenerate Oomycetes, since a sexual process made some very importand feeble' unicellular mycelium occur in some; or they may be ant observations of the regarded as series of primitive forms Icading up to higher members. Zygomycetes. It is well There is no means of deciding the question. They are usually known that while in some included in Oomycetes, but their simple structure, minute size, forms, e.g. Spordinia, usually uniciliate zoospores, and their negative characters would zygospores are easily objustify their retention as a separate group.

contair less than tained, in others, e.g. most 200 species, chiefly parasitic on or in algae and other water-plants species of Mucos, they or animals, of various kinds, or in other lungi, seedlings, pollen and are very erratic in their higher plants. They are often devoid of hyphae, or put forth fine appearance. This has now protoplasmic filaments into the cells of their hosts. After absorbing been explained by the cell-contents of the latter, which it does in a few hours or days, Blakcslee, who finds that the fungus puts out a sporangium, the contents of which break up the Mucorinae can be into numerous minute swarm-spores, usually one-ciliate, rarely divided into two groups, two-ciliate. Any one of these soon comes to rest on a host-cell, termed homothallic and and either pierces it and cmptics its contents into its cavity, where heterothallic respectively. the further development occurs (Olpidium), or merely sends in In the first group zygodelicate protoplasmic filaments (Rhizophydium) or a short hyphal spores can arise by the tube of, at most, two or three cells, which acts as a haustorium, union of branches from the further development taking place outside the cell-wall of the the same mycelium and host (Chytridium). In some cases resting spores are formed inside so can be produced by the the host' (Chytridium), and give rise to zoosporangia on germina- growth from a single spore; tion. In a few species a sexual process is described, consisting in this group includes Spor the conjugation of similar cells (Zygochytrium) or the union of

From Strasburger's Lehrbuch der Belanik, bay

dinia grandis, Spinellus permission of Gustav Fischer. two dissimilar ones. (Polyphagus). In the development of dis- fusiger, some species of

FIG. 6,- Mucor Mucedo. Different tinct antheridial and oogonial cells the allied Ancylistincae show Mucor, &c. The majority close alliances to Pythium and the Oomycetes. On the other hand, of forms, however, fall stages in the formation and germina

tion of the zygospore.

(Aster Brefeld, the uniciliate zoospores of Polyphagus have slightly amoeboid into the heterothallic movements, and in this and the pseudopodium-like nature of the group, in which the asso. 1-4. 5 trom v. Tavel, Pilze.) protoplasmic processes, such forms suggest resemblances to the ciation of branches from Myxomycetes. Opinions differ as to whether the Chytridineae are de two mycelia different in 1. Two conjugating branches in contact. graded or primitive forms, and the group still needs critical revision. nature is necessary for the 2, Septation of the conjugating cells (a) Many new forms will doubtless be discovered, as they are rarely formation of zygospores.

from the suspensors (b). collected on account of their minuteness. Some forms cause damping These structures cannot 3, More advanced stage, the conjugatoff of seedlings-2.8. Olpidium Brassicae; others discoloured spots then be produced from the

ing cells (c) are still distinct from and even tumour-like swellings-e.g. Synchylium Scabiosae, s. product of a single spore

one another; the warty thickenings Succisae, Urophlyctis, &c., on higher plants. Analogies have been nor even from the thalli of their walls have commenced to pointed out between Chytridiaceae and unicellular algae, such as derived from any two

form. Chlorosphaeraceae, Protococcaceae. “ Palmellaccae," &c., some of spores. The two kinds of 4, Ripe zygospore (b) between the sus which are parasitic, and suggestions may be entertained as to thalli Blakeslee considers pensors (@). possible origin from such algae.

to have a differentiation 5, Germinating zygospore with a germThe Zygomyceles, of which about 200 species are described, are of the nature of sex and tube bearing a sporangium. especially important from a theoretical standpoint, since they fur- he distinguishes them as (+) and (-) forms; the former being nished the series whence Brefeld derived the vast majority of the usually distinguished by a somewhat greater luxuriance of growth. fungi. They are characterized especially by the zygospores, but The classification of the Mucorini depends on the prevalence and the asexual organs (sporangia) exhibit interesting series of changes, characters of the conidia, and of the sporangia and zygospores-4.g. beginning with the typical sporangium of Mucor containing numerous the presence or absence of a columella in the former, the formation endospores, passing to cases where, as in Thamnidium, these are of an investment round the latter. Most genera are sa prophytes. accompanied with more numerous small sporangia (sporangioles) but some-Chaetocladium, Piptocephalis-are parasites on other where the sporangioles form but one spore and fall and germinate of tomatoes and other fruits, bulbs, &c., the fleshy parts of which as a whole; that is to say, the monosporous sporangium has become are rapidly destroyed if once the hyphae gain entrance. Even more a conidium, and Brefeld regarded these and similar series of changes important is the question of mycosis in man and other animals, as explaining the relation of ascus to conidium in higher fungi. referred to species of Mucor, and investigated by Lucet and CoAccording to his view, the ascus is in effect the sporangium with stantin. Klebs has concluded that transpiration is the important several spores, the conidium the sporangiole with but one spore, factor in determining the formation of 'sporangia, while zygote. and that not loose but fused with the sporangiole wall. On this development depends on totally different conditions; these results basis, with other interesting morphological comparisons, Brefeld have been called in question by Falck. erected his hypothesis, now untenable, that the Ascomycetes and The Entomophthoraceae contain three genera, Empusa. Ento Basidiomycetes diverge from the Zygomycetes, the former having mophthora and Basidiobolus. The two first genera consist of forms particularly specialized the ascus (sporangial) mode of reproduction, which are parasitic on insects. Empusa Muscae causes the well. the latter having specialized the conidial (indehiscent one-spored known epidemic in house-fies during the autumn; the dead, affected sporangiole) mode. In addition to sporangia and the conidial spores Aies are often found attached to the window surrounded by a white referred to some Mucorini show a peculiar mode of vegetative halo of conidia. B. ranarum is found in the alimentary canal of the reproduction by means of gemmae or chlamydosporesme. short frog and growing on its excrement. In these three genera the conidia segments of the hyphae become stored with fatty reserves and act are cast off with a jerk somewhat in the same way as the sporangium as spores. The gemmae formed on submerged Mucors may bud like of Pilobolus.is bersama Pozrite si ferd

to

B. HIGHER FUNGI.--Now that Brefeld's view of the origin | 32 and 64. &c.; in a few cases the number of spores is less than of these forms from the Zygomycetes has been overthrown, eight by abortion of some of the eight nuclei. The ascus is thus one the relationship of the higher and lower forms of fungi is left of the most sharply characterized structures among the fungi. in obscurity. The term Eumycetes is sometimes applied to this (Sphaerotheca, Pyronema, &c.), in others the antheridium is abortive group to distinguish them from the Phycomycetes, but as the or absent, but the ascogonium (pogonium) is still present and the same name is also applied to the fungi as a whole to differentiate female nuclei fuse in pairs (Lachnea. them from the Mycetozoa and Bacteria, the term had best be bolus furfuraceus):

şlercorca, Humaria granulata, Asco

while in other dropped. The Higher Fungi fall into three groups: the Usti- forms ascogonium and antheridium laginales, of doubtful position, and the two very sharply marked are both absent and fusion occurs groups Basidiales and Ascomyceles.

between vegetative nuclei (Humaria 1. Ustilaginales.--This includes two families Ustilaginaceae of other forms). In other cases the

rutilans, and probably the majority (smuts) and Tilletiaceae (bunts). The bunts and smuts which sexual fusion is apparently absent damage our grain and lodder plants comprise about 400 species of altogether, as in Exoascus. In the first А internal parasites, found in all countries on herbaceous plants, and

case (fig. 9) we have a true sexual especially on Monocotyledons. They are remarkable for their dark

process, while in the second and third spores developed in gall-like excrescences on the leaves, stems, &c.,

cases we have a reduced sexual process or in the fruits of the host. The discovery of the yeast-conidia of in which the fusion of other nuclei these fungi, and their thorough investigation by Brefeld,, have has replaced the fusion of the normal thrown new lights on the group, as also have the results elucidating male and female nuclei. It is to be the nature of the ordinary dark spores--smuts, bunt &c.—which by noted that all the forms exhibit the their mode of origin and development are chlamydospores. When fusion of nuclei in the ascus, so that

B the latter germinate a slender" promycelium is put out: in those with the normal or reduced From Strasburger's Lehrbuch der Ushilago and its allies this is transversely septate, and bears lateral sexual process described above have Botanik, by permission of Gustav conidia (sporidia); in Tilleria and its allies non-septate, and bears

Fischer.

two nuclear fusions in their lifea terminal tuft of conidia (sporidia) (fig. 7); Brefeld regarded the history. The advantage or signifi. Fig. 8.--Development of the promycelium as a kind of basidium, bearing lateral or terminal

Ascus.
conidia (comparable

cance of the second (ascus) fusion is
basidio-
not clearly understood.

A-C, Pyronema confluens.
spores), but since the number of
The group of the Hemiasci was

(Aster Harper.) basidiospores is not fixed, and the founded by Brcfeld to include forms D, Young ascus of Boubasidium has not yet assumed very which were supposed to be a connect.

diera with eight spores. definite morphological characters, ing link between Phycomycetes and

(After Claussen.pores.
Brefeld termed the group Hemi Ascomycetes. As mentioned before,
basidii, and regarded them as a half- the connexion between these two groups is very doubtful, and the de-
way stage in the evolution of the rivation of the ascus from an ordinary sporangium of the Zygomycetes
true Basidiomycetes from Phyco- cannot be accepted. The majority of the forms which were formerly
mycetes, the Tillelio type leading included in this group have been shown to be either true Phycomycetes
to the truc basidium (Autobasidium),(like Ascoidea) or truc Ascomycetes (like Thelebolus). Eremascus and
the. Ustilago, type to the proto-Dipodascus, which are often placed among the Hemiasci, possibly do

basidium, with lateral spores; but this not belong to the Ascomycetes series at all.
pm
view is based on very poor evidence,

Exoascaceae are a small group of doubtful extent here used to so that it is best to place these forms include Exoascus, Taphrina, Ascorlicium and Endomyces. The as a separate group, the Ustilaginales.

The yeast-conidia, which bud off
B.

from the conidia or their resulting

mycelium when sown in nutrient From Vine's Students' Text Book ol solutions, are developed in succesBolany, by permission of Swan Sonnen- sive crops by budding exactly as

in the yeast plant, but they cannot FIG. 7.-Germinating rest- ferment sugar solutions. It is the ing-gonidia. A, of Uslilago rapid spread of these yeast-conidia receptaculorum: B, of Tilletia in manure and soil waters which Caries.

makes it so difficult to get rid of sp, Thc gonidium.

smuts, &c., in the fields, and they, pm, The promycelium. like the ordinary conidia, readily d, The sporidia: in B the infect the seedling wheat, oats,

sporidia have coalesced barley or other cereals. Insection in pairs at v.

in these cases occurs in the seedling

at the place where root and shoot meet, and the infecting hypha having entered the plant goes on living in it and growing up with it as if it had no parasitic action at all. When the flowers form, however, the mycelium sends hyphae into the young ovaries and rapidly replaces the stores of sugar and starch, &c., which would have gone to make the grain, by the soot-like mass of

From Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer. spores so well known as smut, &c. These spores adhere to the grain, FIG. 9.-Sphaerotheca Castagnei. Fertilization and Development and unless destroyed, by " steeping" or other treatment, arc sown

of the Perithecium. (Aster Harper.) with it, and again produce sporidia and yeast-conidia which infect

I, Oogonium (og) with the an. 5. Fertilized oogonium the seedlings. In other species the infection occurs through the style of the power, but the fungus after reaching the ovule develops

theridial branch (az) applied rounded by two layers of

to its surface. no further during that year but remains dormant in the embryo

hyphae derived from the of the seed. On germination, however, thc fungus behaves in the

stalk-cell (st).

2. Separation of antheridium same way as one which has entered in the seedling stage.

The
(an).

6, The multicellular ascogonium

derived by division from the citology of these forms is very little known; Dangcard states that 3. Passage of the antheridial there is a fusion of two nuclei in the chlamydospore, but this requires

nucleus towards that of the oogonium; the terminal cell confirmation. Apart from this observation there is no other trace

pogonium.

with the two nuclei (as) of sexuality in the group.

4. Union of the nuclci.

gives rise to the ascus. II. Ascomycetes. This, except in the case of a few of the simpler forms, is a very sharply marked group characterized by a special mycelium is very much reduced in extent. The asci are borne type of sporangium, the ascus. In the development of the ascus we directly on the myoclium and are therefore fully exposed, being find two nuclei at the base which fuse together to form the single devoid from the beginning of any investment. The Taphrincae, nucleus of the young ascus. The single nucleus divides by three which include Exoascus and Taphrina, are important parasites-successive divisions to form cight nuclei lying free in the protoplasme.g, pocket-plums and witches' brooms on birches, &c., are due to of the ascus. Then by a special method, described first by Harper, their action (fig. 10). Exoascus and Ascorlicium present interesting a mass of protoplasm is cut out round each nucleus; thus cight parallels to Exobasidium and Corlicium among the Basidiomycetes. aninucleate ascospores are formed by free-cell formation. The Saccharomycetaceae include the well-known yeasts which belong protoplasm remaining over is termed epiplasm and often contains mainly to the genus Saccharomyces. They are characterized by glycogen (fig. 8). In some cases nuclear division is carried further their unicellular nature, their power of rapid budding, their capacity before spore formation occurs, and the number of spores is then 16, for fermenting various sugars, and their power of forming endogenous

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spores. The sporangium with its endogenous spores has been and others have shown that a ferment (zymase) can be extracted compared with an ascus, and on these grounds the group is placed from yeast-cells which causes sugar to break up into carbon dioxide among the Ascomycetes a very doubtful association. The group and alcohol. It has since been shown by Buchner and Albert that has attained an importance of late even beyond that to which it was yeast-cells which have been killed by alcohol and ether, or with brought by Pasteur's researches on alcoholic fermentation, chiefly | acetone, still retain the enzyme. Such material is far more active owing to the exact results of the investigations of Hansen, who than the zymase obtained originally by Buchner from the expressed first applied the methods of pure cultures to the study of these juice of yeast-cells. Thus alcoholic fermentation is brought into line organisms, and showed that many of the inconsistencies hitherto with the other sermentations.

cxisting in the literature were Schizosaccharomyces includes a few species in which the cells do
due to the coexistence in the not "bud " but become clongated and then divide transversuly,
cultures of several species or In the formation of sporangia two cells fuse together by means of
races of yeasts morphologically outgrowths, in a manner very similar to that of Spirogyra; sometimes,
almost indistinguishablc. but however, the wall between two cells merely breaks down. The
physiologically very, different. fused cell becomes a sporangium, and in it eight spores are developed.
About fifty species of Saccharo In certain cases single cells develop parthenogenetically, without
myces are described more or less fusion, cach cell producing, however, only four spores." In Zygo-
completely, but since many of saccharomyces described by Barker (1901) we have a form of the
these cannot be distinguished usual sprouting, type, but here again there is a fusion of two cells to
by the microscope, and some form a sporangium.
have been found to develop Cytology.-The study of the nucleus of yeast-cells is rendered
physiological faces of varieties difficult by the presence of other dceply staining granules termed by

under special conditions of Guillermond melachromatic granules. These have often been miscut

growth, the limits are still far taken for nuclei and have to be carefully distinguished by differential

ill-defined for complete stains. In the process of budding the nucleus divides apparently -ep

botanical treatment of the genus. by a process of direct division. In the formation of spores the nucleus A typical yeast is able to develop of the cell divides, the protoplasm collects round the nuclei to form new cells by budding when sub the spores by free-cell 'formation; the protoplasm (epiplasm) not

merged in a saccharine solution, used in this process becomes disorganized. A fusion of nuclei was From Strasburger's Lehrbuch der

and to ferment the sugar-ic. originally described by Jansens and Leblanc, but it was observed Bolanık, by permission of Gustav Fischer.

so to break up its molecules that, neither by Wager nor Guillermond and is probably absent. In

apart from small quantities used Schizosaccharomyces and Zygosaccharomyces, however, we have a Fig. 10.--Taphrina Pruni: for its own substance, masses of lusion of nuclei in connexion with the conjugation of cells which Transverse section through the it out of all proportion to the precedes sporangium-formation. The theory may be put forward epidermis of an infected plum. mass of yeast used become that the ordinary forms have been derived from sexual forms like Four ripe asci, 21. az, with eight resolved into other bodies, such Schizosaccharomyces and Zygosaccharomyces by a loss of sexuality, spores, ., with yeast-like as carbon dioxide and alcohol, the sporangium being formed parthenogenetically without any conidia abstricted from the spores. the process requiring little or nuclear fusion. This suggests a possible relationship to Eremascus, After Sadebeck.

no oxygen. Brefeld regards the which can only doubtfully be placed in the Ascomycetes (vide supra). sl, Stalk-cells of the asci. Filaments of the mycelium tion of conidia.

budding process as the forma Carpoascomyceles.-The other divisions of the Ascomycetes may

Under other be distinguished as Carpoascomycetes because they do not bear cut transversely.

conditions, of which the tempera- the asci free on the mycelium but enclosed in definite fruit bodies cul, Cuticle.

ture is an important one, the or ascocarps. The ascocarps can be distinguished into two portions, cp. Epidermis.

nucleus in the yeast-cell divides, a mass of sterile or vegetative hyphae forming the main mass of the

and each daughter-nucleus again, fruit body, and surrounding the fertile ascogenous hyphae which and lour spores are formed in the mother cell, a process obviously com bear at their ends the asci. When the ascogonium (female organ) parable to the typical development of ascospores in an ascus. Under is present the ascogenous hyphae arise from it, with or without its yet other conditions the quiescent yeast-cells floating on the surface previous susion with an antheridium. In other cases the ascogenous of the fermented liquor grow out into elongated sausage-shaped or hyphac arise directly from the vegetative hyphac. In connexion cylindrical cells and branching cell-series, which mat together into with this condition of reduction a fusion of nuclei has been observed mycelium-like veils. At the bottom of the fermented liquor the in Humaria rutilans and is probably of frequent occurrence. The cells often obtain fatty contents and thick walls, and behave as asci may be derived from the terminal cell of the branches of the resting cells (chlamydospores). The characters employed by experts ascogenous hyphae, but usually they are derived from the penfor determining a specics of ycast are the sum of its peculiaritics as ultimate cell, the tip curving over to form the so-called crozier. By regards form and size: the shapes, colours, consistency, &c., of this means the ascus cell is brought uppermost, and after the fusion the colonies grown on certain definite mcdia; the optimum tem- of the two nuclei it develops enormously and produces the ascospores. perature for spore-formation, and for the development of the The ascospores escape from the asci in various ways, sometimes by veils '; and the behaviour as regards the various sugars.

a special ejaculation-mechanism. The Ascomycetes, at least the The following summary of some of the principal characteristics Carpoascomycetes, exhibit a well-marked alternation of sexual and of hall-a-dozen species will serve to show how such peculiarities can asexual generations. The ordinary mycelium is the gametophyte be utilized for systematic purposes:

since it bears the ascogonia and antheridia when present; the Species. Optimum Temperature for

Characters of

Sugars Fermented and Spores. Veils. Fermentation. Cells. Spores.

Products, &c
S. cereviseae I.

20°-28°
High Rounded Globoid

Inverts maltose and sac S. Pastorianus I. 270-5° 26-28°

Low
Rounded Globoid

charose and form alcohol S. ellipsoideus

33°-349

Low
Rounded Globoid

4-6 vol.%. S. anomalus

Ditto, and evolves a fra? High Elliptical Hat-shaped

grant ether. S. Ludwigii

?

?
Elongated Globoid

Will not invert maltose. S. membranaefaciens

?
High

Inverts neither maltose nor
Elongated Globoid

saccharose. Two questions of great theoretical importance have been raised ascogenous hyphac with their asci represent the sporophyte since over and over again in connexion with yeasts, namely: (1) the they are derived from the fertilized ascogonium. The matter is morphological one as to whether yeasts are merely degraded forms complicated by the apogamous transition from gametophyte to of higher fungi, as would seem implied by their tendency to form sporophyte in ihe absence of the ascogonium; also by the fact that elongated, hypha-like cells in the veils, and their development there are normally two fusions in the life-history as mentioned of "ascospores as well as by the wide occurrence of yeast-like carlier. If there are two fusions one would expect two reductions,

sprouting forms " in other fungi (e.8. Mucor, Exoasci, Ustilagineae, and Harper has suggested that the division of the nuclei into eight higher Ascomycetes and Basidiomycetes); and (2) the question as in the ascus, instead of into four spores as in most reduction proto the physiological nature and meaning of fermentation. With cesses, is associated with a double reduction process in the ascus. regard to the first question no satisfactory proof has as yet been Miss Fraser in llumaria rutilans finds two reductions: a normal given that Saccharomycetes' are derivable by culture from any synaptic reduction in the first nuclear division of the ascus, and a higher form, the recent statements to that effect not having been peculier reduction division termed bruchymciosis in the third ascus confirmed. At the same time there are strong grounds for insisting division. on the resemblances between Endomyces, a hyphal fungus bearing Various types of ascocarp are characteristic of the different yeast-like asci, and such a form as Saccharomyces anomalus. Con divisions of the Carpoascomycetes: the cleistothecium, apothecium cerning the second question, the recent investigations of Buchner and perithecium.

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Perisporinęge. This includes two chief families, Erysiphaceae characterized in general by the possession of an ascocarp which, and Perisporiaceae. They are characterized by an ascocarp without though usually a completely closed structure during the earlier any opening to the exterior, the ascospores being set free by the stages of development, at maturity opens out to form a bowl or decay or rupture of the ascocarp wall; such a fruit-body is termed saucer-shaped organ, thus completely exposing the layer of asci a cleistothecium (cleistocarp). "The Erysiphaceae are a sharply which forms the hymenium. Such an ascocarp goes by the name of marked group of forms which live as parasites. They form a super-apothecium. Owing to the shape of the fruit-body many of these ficial mycelium on the surface of the plant, the hyphae not usually forms are known as cup-fungi, the cup or apothecium often attaining penetrating the tissues but merely sending haustoria into the

epi- a large size, sometimes several inches across (fig. 12). Functional dermal cells. Only in rare cases is the mycelium intercellular. male and female organs have been shown to exist in Pyronema and Owing to their appearance they go by the popular name of mildews. Boudiera; in Lachnea stercorea slo

do mal Sphaerotheca Humuli is the well known hop-mildew, Sphaerotheca both ascogonia and antheridia

a s madlo Mors-Uvae is the gooseberry mildew, the recent advent of which are present, but the antheridiumiw qon

od yw has led to special legislation in Great Britain to prevent its spreading, is non-functional, the ascogonialog

Isiroga as when rampant it makes the culture of gooseberries impossible. (female) nuclei fusing in pairs; Erysiphe, Uncinula and Phyllactinia are other well-known genera. this is also the case in Humaria The form of the fruit body, the difference and the nature of special granulata and Ascobolus furfur: outgrowths upon .it-the appendages-are characteristic of the aceus, where the antheridium is various genera. Besides peritheca the members of the Erysiphaceae entirely absent. In H. rutilans, possess conidia borne in simple chains. De Bary brought forward however, both sexual organs are very strong evidence for the origin of the ascocarp in Sphaerotheca absent and the ascogenous and Erysiphe by a sexual process, but Harper in 1895 was the first hyphae arise apogamously from to prove conclusively, by the observation of the nuclear fusion, that the ordinary hyphae of the mythere was a definite fertilization in Sphaerotheca Humuli by the celim. In all these cases the c. fusion of a male (antheridial) nucleus with a female, ascogonialallgau 20 Logeen luoda (oogonial) nucleus. Since then Harper has shown that the same Soblebning process occurs in Erysiphe and Phyllactinia.

salt The Perisporiaceae are saprophytic forms, the two chief genera being Aspergillus and Penicillium. The blue-green mould P.

One Cool bus

2 crustaceum and the green mould A. herbariorium (= Eurotium

TO herbariorum) are extraordinarily widely distributed, moulds being

30.90 found on almost any food-material which is exposed to the air.

engrossFig. 13.- Ascobolus furfuraceus. They have characteristic conidiophores bearing numerous conidia,

Cobra Diagrammatic section of the frucand also cleistothecia which are spherical in form and yellowish in

za tification. (After Janczewski.) colour. The latter arise from the crown of a spirally coiled archicarp

San
m, Mycelium.

mor (bearing an ascogonium at its end) and a straight antheridium.

Lehr

579 To Vegetative hyphae then grow up and surround these and enclose buch der Botanik, by percetis pain Pollinodium. una them in a continuous sheath of plectenchyma (fig. 11). It has lately sion of Gustav Fischer. been shown by Fraser and Chambers that in Eurolium both

Sy Ascogenous filaments.
FIG. 12.-Pezisa aur-

(oltro
antiaca. (After Kromb-

Þ, The sterile tissue from which D holz, nat. size.)

the paraphyses k spring. ascogonium and antheridium contain numerous nuclei; they are to be looked upon as gametangia in which there is no differentiation of gametes, and since they act as single gametes they are termed coenogametes. In some forms as in Ascobolus the ascogonium is multicellular, the various cells communicating by pores in the transverse walls (fig. 13).

In the Helvellaceae there is no apothecium but a large 'irregular fruit body which at maturity bears the asci on its surface. The development is

only slightly known, but there Len Din A

is some evidence for believing

that the fruit-body is closed in snobber

its very carly stages. be

The genus Peziza (in its (do 1919 12

widest sense) may be taken as Stogel

the type of the group. Most

of them grow on living plants 1931A).

or on dead vegetable remains, H

very often on fallen wood; a

number, however, are found TO A HOT by Hoa

do

growing on earth which is rich 197 ned

STUS:
Band

in humus. The genus ScleroBib FIG. 11.- Development of Eurotium repens. (After De Bary.)

linia may be mentioned here; 04 with conidiophore (c), and E, F, Sections of young peri- conidia are fragrant and are A, Small portion of mycelium D, The perithecium.to a number of forms have been young archicarp (as).

thecia.

carried by bees to the stigma wol B, The spiral archicarp (as), w, Parietal cells. ' with the antheridium (s).

of the bilberry; here they f. Pseudo-parenchyma.

germinate with the pollen and D, The same, beginning to be as, Ascogonium.

the
hyphae pass with the pollen by permission of Gustav Fischer.

From Strasburger's Lehrbuch der Bolanik, Arcsurrounded by the hyphae G, An ascus.

tubes down the style; the forming the perithecium wall. H, An ascospore.

former infect the ovules and spora fimiseda in longitudinal section

FIG: 14.-Perithecium of Podoproduce sclerotia, therein re

After v. Tavel. ascogonium and antheridium contain a number of nuclei (i.e. are ducing the fruits to a mum

S,

Asci. coenogametes), but that the antheridium disorganizes without mified condition. From the passing its contents into the ascogonium. There is apparently a sclerotia

later the apothecium , Paraphyses. egin dobro

blandt nuclei in pairs. Aspergillus Oryzae plays an important part in heteroica, is heteroecious; the m, Mycelial hyphae. a Lumen saccharifying the starch of rice, maize, &c.,

by means of the abundantascospores infecting the leaves of Vaccinium uliginosum, while the diastase it secretes, and, in symbiosis with a yeast which ferments conidia which then arise infect only Ledum palustre. This is the the sugar formed, has long been used by the Japanese for the pre-only case of heteroecism known in the vegetable kingdom outside paration of the alcoholic liquor saké. The process has now been the Uredineae. successfully introduced into European commerce.

Pyrenomycetes. This is an extraordinarily large and varied group Discomycetes.-Used in its widest sense this includes the of forms which mostly live parasitically or saprophytically on Hysteriaceae, Phacidiaceae, Helvellaceae, &c. The group is vegetable tissue, but a few are parasitic on insect-larvae. The group

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is characterized by a special type of ascocarp, the perithecium. This nuclear association of equivalent nuclei apparently represents This is typically of a flask-shaped form opening with

a small pore at a reduced sexual process (like the fusion of female nuclei in Humaria the top. The asci live at the bottom often mixed with paraphyses, granulata and of vegetative nuclei in H rutilans, among the Asco while the upper "neck" of the flask is lined with special hyphae, mycetes) in which, however, the actual fusion (normally, in a sexual the periphyses, which aid in the ejection of the spores (fig. 14). process, occurring immediately after association) is delayed until The simpler

forms bear the perithecia directly on the mycelium, but the formation of the basidium. During the tetrad division in the the more highly developed forms often bear them on a special basidium nuclear reduction occurs. There is thus in all the Basidiales mycelial development-the stroma, which is often of large size and an alternation of generations, obscured, however, by the apogamous special shape and colour, and of dense consistence. The cytological transition from the gametophyte to sporophyte. The sporophyte details of development of the perithecia are not well known; most may be considered to begin at the stage of nuclear association and of them appear to develop their ascogenous hyphae in an apogamous end with the nuclear reduction in the basidium. way without any connexion with an ascogonium. Besides the Uredineae. - This is a large group of about 2000 forms. They are special ascocarps, accessory reproductive organs are known in the all intercellular parasites living mostly on the leaves of higher majority of cases in the form of conidia.lu

plants. Owing to the presence of oily globules of an orange-yellow Í uberinede.-These are a small group of fungi including the well or rusty-red colour in their hyphae and spores they are termed known truffles. They are found living saprophytically in part Rust-Fungi. They are distinguished from the other fungi and the parasitically) underground in forests. The asci are developed in rest of the Basidiales by the great variety of the spores and the the large dense fruit bodies (cleistothecia) and the spores escape by great elaboration of the life-history to be found in many cases. the decay of the wall. The fruit-body is of complicated structure, Five different kinds of spores may be present-teleutospores, but its early stages of development are not known. Many of the sporidia (= basidiospores), aecidiospores, spermatia and uredospores fruit-bodies have a pleasant flavour and are eaten under the name of (fig. 16). The teleutospore, with the sporidia which arise from it, truffles (Tuber brumale and other species). The exact life-history is always present, and the division into genera is based chiefly on of the truffle is not known.

Laboulbeniineae are a group of about 150. species of fungi found nodas la on insects, especially beetles, and principally known from the relevant searches of Thaxter in America. The plant is a small, dark brown,

BB

019 erect structure (receptacle) of a few cells, and 1-10 mm. high, attached paar sp to the insect by the lowermost end (foot),

and easily mistaken for a blue hair or similar appendage of the insect. The receptacle ends above in appendages, each consisting of one or a few cells, some of which als are the male organs, others the female organs, and others again may be barren hairs. The male organ (antheridium) consists of a few in FOTO cells, the terminal one of which either abstricts from its end, or emits they be from its interior the non-motile spermatia, reminding us of those paber

lo of the Florideae. The female organ is essentially a flask-shaped the

133 structure; the neck of the flask growing out as the trichogyne, and cold brez the belly composed of an axial carpogenic cell surrounded by investing cells, and with one cell (trichophoric) between it and the tricho-roll

world gyne. These three elements—tríchogyne, trichophoric cell, and carpogenic cell-are regarded as the procarp. The spermatia have been shown by Thaxter to fuse with the trichogyne, after which the axial cell below (carpogenic cell) undergoes divisions, and ultimately forms asci containing ascospores, while cells investing this form a perithecium, the whole structure reminding us essentially of the fructification of a Pyrenomycete. Many modifications in details

occur, and the plants may be
dioecious. No injury is done to
the infested insects. It has lately
been shown that there is a fusion
of nuclei in connexion with ascus
formation, so that chere can be
no doubt of the position of this
extraordinary group of plants
among the Ascomycetes. The
various cells of these organisms

Wus.se
are connected by large pits

FIG. 16.--Puccinia graminis.
which are traversed by thick
B

protoplasmic threads connecting A, Mass of teleutospores (1) on a vulgaris, with a, aecidium
one cell with the next. In this leaf of couch-grass.

fruits, P. peridium, and 5p. point and in their method of €, Epidermis ruptured.

spermogonia. (After Sachs.) fertilization the Laboulbeniineaeb, Sub-epidermal fibres. (After C, Mass of uredospores (ur). suggest a possible relationship

De Bary.)

with one teleutospore (c)

of vertical section sh, Sub-hymenial hyphae. (After From Strasburger's Lehrbuch der Betanik, of Ascomycetes and the Red B, Part Algae.

through leaf of Berberis De Bary.)
by permission of Gustav Fischer
FIG. 15.-Armillaria mellea. (After

Basidiales.-This very large
Ruhland.)

group

of plants is characterized its characters. The teleutospore puts forth on germination a fourA, Young basidium with the two by the possession of a special celled structure, the promycelium or basidium, and this bears later primary nuclei.

type of conidiophore-the bas-four sporidia or basidiospores, one on each cell. When the sporidia B, After fusion of the two nuclei. idium, which gives its name to infect a plant the mycelium so produced

gives origin to aecidiospores Hypholoma appendiculatum.

the group. The basidium is and spermatia; the aecidiospores on infection produce a mycelium C. A basidium before the four a unicellular or multicellular which bears uredospores and later teleutospores. This is the lifeary nucleus of the basidium idiospores arise as outgrowths; In the opsis forms the uredospores are absent, the

mycelium from the have passed into the four but soon, like the ascus, becomes hemi the aecidiospores are absent, the mycelium from the sporidia D. Passage of a nucleus through two nuclei. Then two successive matia, in the latter they are absent. In lepto and micro forms both

the sterigma into the basidio- nuclear divisions occur resulting aecidiospores and uredospores are absent, the sporidia producing a spore.

in the formation of four nuclei mycelium which gives rise directly to teleutospores; in the lepto which later migrate respectively into the four basidiospores (fig. 15), forms the teleutospores can germinate directly, in the micro forms The Basidiales are further characterized by the complete loss of only after a period of rest. We have thus a series showing a progres. normal sexuality, but at some time or other in the life-history sive reduction in the complexity of the life-history, the lepto and there takes place an association of two nuclei in a cell; the two micro forms having a life-history like that of the Basidiomycetes. nuclei are derived from separate cells or possibly in some cases are The eu and opsis forms may exhibit the remarkable phenomenon sister nuclei of the same cell. The two nuclei when once associated of heteroecism, i.e. the dependence of the fungus on two distinct are termed "conjugate" nuclei, and they always divide at the same host-plants for the completion of the life-history. Heteroecism time, a half of each passing into each cell. This conjugate

condition is very common in this

group and is now known in over one hundred is finally brought to a close by the nuclear fusion in the basidium. and fifty species. In all cases of heteroecism the sporidia infect Between the nuclear association and the nuclear fusion in the one host leading to the production of aecidiospores and spermatia basidium many thousands of cell generations may be intercalated. (if present), while the aecidiospores are only able to infect another

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