any fluid through the bark; and any body which contains much moisture be applied, numerous roots will soon be emitted into it immediately above the decorticated space, but never immediately beneath it and when the alburnum in the decorticated spaces has become lifeless to a considerable depth, buds are usually protruded beneath, but never immediately above it, apparently owing to the obstruction of the ascending sap. The roots, which are emitted in the preceding case, do not appear in any degree to differ from those which descend from the radicles of generating seeds, and both apparently derive their matter from the fluid which descends through the cortical vessels.

There are several varieties of the apple tree, the trunks and branches of which are almost covered with rough excrescences, formed by congeries of points which would have become roots under favourable circumstances; and such varieties are always very readily propagated by cuttings. Having thus obtained a considerable number of plants of one of these varieties, the excrescences began to form upon their stems when two years old, and mould being then applied to them in the spring, numerous roots were emitted into it early in the summer. The mould was at the same time raised round, and applied to, the stems of other trees of the same age and variety, and in every respect similar, except that the tops of the latter were cut off a short distance above the lowest excrescence, so that there were no buds or leaves from which sap could descend to generate or feed new roots; and under these circumstances no roots, but numerous buds were emitted, and these buds

all sprang from the spaces and points, which under different circumstances had afforded roots. The tops of the trees last mentioned, having been divided into pieces of ten inches long, were planted as cuttings, and roots were by these emitted from the lowest excrescences beneath the soil, and buds from the uppermost of those above it.

I had anticipated the result of each of the preceding experiments; not that I supposed, or now suppose, that roots can be changed into buds, or buds into roots; but I had before proved that the organization of the alburnum is better calculated to carry the sap it contains, from the root upwards, than in any other direction, and I concluded that the sap when arrived at the top of the cutting through the alburnum would be there employed, as I had observed in many similiar cases, in generating buds, and that these buds would be protruded where the bark was young and thin, and consequently afforded little resistance. I had also proved the bark to be better calculated to carry the sap towards the roots than in the opposite direction, and I thence inferred that as soon as any buds, emitted by the cuttings, afforded leaves, the sap would be conveyed from these to the lower extremity of the cuttings by the cortical vessels, and be there em. ployed in the formation of roots.

Both the alburnum and bark of trees evidently contain their true sap; but whether the fluid which ascends in such cases as the preceding through the alburnum to generate buds, be essentially dif ferent from that which descends down the bark to generate roots, it is perhaps impossible to decide. As nature, however, appears in the vegetable

vegetable world to operate by the simplest means; and as the vegetable sap,like the animal blood, is probably filled with particles which are endued with life, were I to offer a conjecture, I am much more disposed to believe that the same fluid, even by merely acquiring different motions, may generate different organs, than that two distinct fluids are employed to form the root, and the bud and leaf.

When alburnum is formed in the root, the organ possesses, in common with the stem and branches, the power of producing buds, and of emitting fibrous roots, and when it is detached from the tree, the buds always spring near its upper end, and the roots near the opposite extremity, as in the cuttings abovementioned. The alburnum of the root is also similar to that of other parts of the tree, except that it is more porous, probably owing to the presence of abundant moisture during the period in which it is deposited. And possibly the same cause may retain the wood of the root permanently in the state of alburnum; for I have shewn, in a former memoir, that if the mould be taken away, so that the parts of the larger roots, which adjoin the trunk, be exposed to the air, such parts are subsequently found to contain much heart wood. I would wish the preceding observations to be considered as extending to trees only, and exclusive of the palm tribe; but I believe they are nevertheless generally applicable to perennial herbaceous plants, and that the buds and fibrous roots of these originate from substances which correspond with the alburnum and bark of trees. It is obvious, that the roots which bulbs emit in the spring, are generated by the sap which descends

from the bulb, when that retains its natural position; and such ta berous rooted plants as the potatoe offer rather a seeming than a real obstacle to the hypothesis I am endeavouring to establish. The buds of these are generally formed beneath the soil; but I have shewn, in a former memoir, that the buds on every part of the stem may be made to generate tubers, which are similar to those usually formed beneath the soil; and I have subsequently seen, in many instances, such emitted by a re-produced bud, without the calix of a blossom, which had failed to produce fruit; but I have never, under any circumstances, been able to obtain tubers from the fibrous roots of the plant.

The tube therefore appears to differ little from a branch, which has dilated instead of extending itself, except that it becomes capable of retaining life during a longer period; and when I have laboured through a whole summer to counteract the natural habits of the plant; a profusion of blossoms has in many instances sprung from the buds of a tuber.

The runners also, which, according to the natural habit of the plant, give existence to the tubers beneath the soil, are very similar in organization to the stem of the plant, and readily emit leaves and become converted into perfect stems, in a few days, if the current of ascending sap be diverted into them; and the mode in which the tuber is formed above, and beneath the soil, is precisely the same. And when the sap, which has been deposited at rest during the autumn and winter, is again called into action to feed the buds, which elongate into parts of the stems of the future plants in the spring,

Abrons

fibrous roots are emitted from the bases of these stems, whilst buds are generated at the opposite extremities, as in the cases I have mentioned respecting trees.

Many naturalists have supposed the fibrous roots of all plants to be of annual duration only; and those of bulbous and tuberous rooted plants certainly are so; as in these nature has provided a distinct reservoir for the sap which is to form the first leaves and fibrous roots of the succeeding season; but the organization of trees is very different, and the a

num

and bark of the roots and tems of these are the reservoirs of their sap during the winter. When; however, the fibrous roots of trees

in the succeeding spring; but I have not observed the same mortality to occur, in any degree, in the roots of trees when growing, under favourable circumstances, in their natural situation.

I am prepared to offer some observations on the causes which direct the roots of plants in search of proper nutriment, and which occasion the root of the same plant to assume different forms under different circumstances; but I propose to make those observations the subject of a future communication.

I am, my dear Sir,
with great respect,
Your much obliged, &c.
T. A. KNIGHT."

"TH

HERE are many uses in the arts and manufactures to which the application of the ammonia or volatile alkali is well known, and which are already in part enumerated. But when the demand for these purposes is supplied, and, on the probable great extent of the production of your ammonia, should a surplus quantity remain, I have reason to think, that in some very considerable departments of agriculture that surplus, however great, will find a ready and adequate market. A judicious application of ammonia to land before it be sown with turnips (but if afterwards, on no account after the plants are up), is likely to produce the most bene

ficial results. What justifies me in this conclusion, is the simple consideration, that all the powerful and concentrated manures of high price, and in great request, are just so in the degree in which I have found them by analysis to contain either ammonia or the elements that compose it. Soot, well known to be in small quantities a powerful encourager of vegetation, contains much carbonate of ammonia, combined with some of the carbonaceous parts, rendering them extractive and soluble in water, forming a brown pungent liquid. Pigeon dung is a dressing for tur nip land in great request in the North, where many hundred quarters are annually sold at 1215. the quarter

quarter, though a very small proportion of the demand is supplied. I have found, by experiment, that this material is richly impregnated with carbonate of ammonia as well as with the well known element of ammonia, azote, which, in the natural decomposition of the manure by putrefaction, when committed to the earth, will be produced. Rape dust is that particular part of the seed (left after the oil is pressed out) which is intended by nature to corrupt, and become the early cause or stimulus of the growth of the embryo germ, and therefore contains the same ⚫lement, and which we can readily, by a chemical process, exhibit in the ammonia which rape dust may be made to yield. It is hardly necessary to mention urine, &c., from which ammonia is obtained in great quantity, or the dung of all animals, which contains the same principle. It was from the dung of the animals which fed on the fertile plains of Egypt that all the sal-ammoniac known in commerce was for many centuries obtained. From that country, the site of the temple of Jupiter Ammon, its name is derived. Soon after sal ammoniac became an article of European manufacture, it was discovered that the bones and horns of animals yielded its pecuJiar salt, that is to say, the ammoniacal principle, in much greater quantity than their dung, and those parts were alone used to the exclusion of these hence the name spirit of hartshorn, given to the volatile alkali used in medicine, It has been of late years discovered, that the scrapings, shavings, and chips of the horns used in ma nufactures (particularly of the knife handles at Sheffield) are the most powerful and the best of all land

dressings known; and it is from these very materials also that the greatest quantity of ammonia is to be obtained, wool, silk, and hair excepted, and these are again in great use in agriculture, when collected and sold as old woollen rags. Bones of all kinds, not excepting human bones, are sent by sea in great quantity from this metropolis into the North; many hundred tons of these are ground, or rather broken small, in mills contrived on purpose, as the quantity necessary for an acre of land is small in comparison of other materials. The convenience of easy carriage is the cause of the most distant lands being brought into the richest culti vation. It would not be proper, on this occasion, to enter into a theoretical disquisition on the nonrishment of vegetables, whether they derive their food wholly, or only in small part, from the earth by their roots, or from the atmosphere by their leaves and green parts; but it appears clear to me, that that principle which the farmers term warmth and force, is constantly accompanied by the chemic element mentioned. This stimulus of encouragement and force is of more consequence to the growth and eventual vigour of an nuals than of perennials, and particularly at the early periods immediately succeeding the expenditure of this sure principle which nature has provided in the seed. The putrefactive fermentation always generates ammonia; the earth imbibes the different miasmata, and holds them in store for the use of plants; to these they impart health, strength, and, as may be said, appetite.

A great difference is observed by farmers in the qualities of the manure of cattle, when fed on oil

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