reducing their number to three or four, or even one division, the same result will ensue.

I beg to observe that no part of the substance of the actual concentric layer (see fig. 4. at g g, and fig. 3. at n n.) is continued into the stalks or leaves; had the ligneous fibres of the concentric layer extended into them, it would have caused the stalks and leaves to have permanently remained upon the trees, after they had performed their summer's office, and appeared an unsightly incumbrance of dry materials; but the whole being of a perishable nature, they drop off as soon as their vital principle ceases to act. What a remarkable instance is this of Nature preserving the beauty of her works, as well as of a further provision that their decomposition or decay should become the future food of plants! We have frequent instances of this fact, by the luxuriant growth of trees in many woods, where the herbage that surrounds such woods, growing on the same kind of soil, is scarcely sufficient to feed a few sheep.

The Liber I shall now partially describe; it is the inward substance of the bark, and joins the alburnum. In a large, healthy, summer shoot of the vine, it will be found to be about one tenth of an inch thick; but, in order to examine it minutely, a very thin slice should be cut from a collet by the little regulating machine, as mentioned before, and moistened with the solution of the sulphate of iron; then, with the assistance of two powerful magnifying glasses connected together, the liber will be distinctly seen; and, upon an attentive examination, it will be found to consist of two bars of ligneous vessels (fig. 4. e e) lying between three bars of other vessels (d d d), which latter appear in their early state to be somewhat of a fleshy elastic substance, but in their more matured state, they become woody, and are nearly hexagonal-shaped vessels. They are only acted upon by the sulphate of iron, from their containing gallic acid, so that the two substances in the liber may be easily distinguished from each other by the black precipitate upon the fleshy vessels d dd, when none will be seen on the ligneous vessels e e.

Fig. 3. represents part of the perpendicular vessels of a division, cut down the middle; ffff are those of the liber, consisting of the three dark and two white lines, similar to those on a larger scale in fig. 4. d d d d, and ee. The liber is invariably placed on the outside of the alburnum, whether in the root, stem, or branch of the vine; but, in the claw, stalk, and leaf, it covers only the ascending sap and spiral vessels. It is the principal agent in forming the alburnum, which will be shown when I explain its gradual growth or increase.

So far my remarks have been directed nearly exclusively to the vessels of a division, to simplify the description of those of a collet; and the vessels have been traced from the collet to the commencement of the claw, as in fig. 3. z, where they are supposed to have extended themselves to the outside of the shoot beyond the other divisions of i k l m.

I will now endeavour to describe the beautiful simplicity by which Nature arranges the union of the continued vessels of six of these divisions to form the stalk and leaf. Fig. 2. represents their outward appearance at ef g h i k, where they form the base of the footstalk of a leaf; and we will further suppose e to have extended itself in a horizontal direction from the place at z fig. 3. toward x in fig 2. As the vessels of one division would not have been sufficient of themselves to form an entire leaf, nor could one set have been placed sufficiently firm on the outside of the joint, those of another division extend themselves in like manner from the opposite side of the joint from k toward as in fig. 2.; these are further added to and strengthened by two others, acting also as claspers, as at ƒ i, and the centre of the base is firmly secured by two more immediately underneath, which give strength to the other four claws, and give also an additional number of vessels at g h. The vessels of the six divisions, when thus united, form the footstalk of the leaf, and, by their further continuation from thence, produce the stalk, as well as the leaf. It is difficult in a drawing like fig. 2. to convey an accurate idea, that the base of the footstalk of the leaf has no support or connection, but from the vessels of the six divisions. On the left hand side of the drawing, a vascular bundle is divested of its cuticle and cellular texture, to show that it runs directly underneath the claw of e, from the bottom to the top; and, on the opposite side, I have represented a spear-pointed knife underneath the two claws i k. Such an operation on the plant would have only cut through its cuticle, but not the perpendicular vessels of the shoot underneath the knife, which are independent of the claws, as much so, as if no part of them had been covered by the claws.

In fig. 2. the outside clasping claws of e and k appear as if they arose from the collet exactly across the centre; but they commence considerably behind, that they may possess more power to hold the base of the stalk of the leaf. In some leaves that have no stalk, but arise immediately from the joint, the claws do not require such extra means to hold them. But where the stalk is very thick and heavy, and the leaves extremely large, as those on the stem of the garden rhubarb (Rheum rhapónticum) gone to seed, their claws nearly touch

each other at the back of the joint. The vessels which compose them proceed from upwards of twenty divisions; they form a circle just within the edge of the stem, and within that circle another is formed belonging to the next leaf above, and within the second are those of the third, &c. Every person interested in this subject I would recommend to examine one of the rhubarb stalks under such circumstances.

That the bundles of the vascular texture of fig. 2., which lie on the outside of the six divisions, and commence at n o p qrs, and join their respective claws above, may be easily distinguished, their cuticle and cellular texture are in fig. 2. removed from them, as well as from the others below the joint, that their general arrangement so far might be seen at one view.

I wish now to draw your attention particularly to those six sets of vessels of the claws e f g h i k, fig. 2., which are a continuation from the six divisions of the collets to the base of the stalk of the leaf. The first layer consists of the cuticle; the second of the cellular texture; the third of the vascular texture, similar to fig. 3. at g g above z; the fourth of the liber at ff above z; the fifth of the ascending sap-vessels of b c d e above z; and the sixth of the spiral vessels at a above z; so that we see by this admirable arrangement the special protection given to the spiral vessels: for they are those which convey the secreted juice from the matured liber to the young extending shoot, previously to the formation of the ascending sap-vessels of the alburnum. The vessels of the medulla are not continued in so distinct a manner as the others, they are formed in the stalk and leaf from the cellular texture of the second layer. No part of the ligneous fibres of the concentric layer of the collet enters into them, for the reasons already given. As the whole of those vessels of the claws are so peculiarly interesting, I shall exhibit them in a future drawing, with further particulars respecting them.

I have been rather short in my description of the liber, considering its great importance to the plant, because the vessels of the vascular texture, which are in bundles, are much more conspicuous, and these two always act in unison together. Some writers have called the whole of the bark the descending vessels; but I consider only those of the liber and the cellular texture to be permanently so in the vine, as I hope fully to explain when I describe the second year's growth of the shoot of fig. 1.

I flatter myself the ascending sap has been satisfactorily shown to pass up the vessels of the alburnum into the leaf, but no proof has yet been given that it proceeds any farther. To prove it, I shall avail myself of the gallic acid, which exists in

the liber of the leaf; this fluid may be easily precipitated by simply placing, in the autumn (previously the vessels are so small that they are choaked up by the precipitate), a shoot of the vine, in a weak solution of the sulphate of iron and, upon standing therein for some time, the thin parts of the leaves will become black, as soon as the union takes place between the ascending sulphate of iron, and the gallic acid of the leaf; it will afterwards descend down the vessels of the liber of the stalk of the leaf, and sometimes down to the liber of the collet, which will in like manner become black: but the ascending vessels of the alburnum of the shoot will not be discoloured, nor the ascending vessels of the stalk of the leaf, because the solution has not met with any gallic acid in its ascent through those vessels.

It is highly gratifying, in our examination of the economy of Nature, to have her assistance in such operation; for no artificial means could have been used to pass a solution into the above minute vessels had they been void of actual life.

By the assistance of these chemical tests, I flatter myself the investigation of the anatomy of vegetation will be facilitated, and I sincerely hope others will prosecute it with greater perseverance; by so doing they will convince themselves how sublimely Nature carries on her grand operations, by a repetition of parts, and those united by the most simple means, as well as by a continuation of those parts subdivided. Although we shall never discover the hidden springs by which she creates, animates, and elongates the living vegetable fibres; yet, by their aid, many interesting facts may be discovered relative to the larger vessels. I have many apologies to make for occupying your time, even in the perusal of this long letter; and I am fearful, also, in addition to the reasons already given of the number of drawings, that the length of my remarks will exclude both from your valuable and instructive Magazine; but this I must leave entirely for your liberality and consideration. I remain, Sir, &c.

Bath, June 12.

WALTER WILLIAM CAPPER.

The common copperas, or sulphate of iron, becomes a stronger test by the following method:

Dry down before the fire, on a plate, 8 oz. of the common copperas of the shops. Reduce it to a fine powder, then weigh 100 grs. of it, which place in a mortar, and add to it 10 drops of nitric acid, mix them well together, afterwards add 4 oz. of water, and filter it. This liquor should be kept closely stopped.

The following is a description of the little regulating machine (fig. 6.), by which thin slices may be cut from the collet, &c.

abcd, The top 1 in. square,

and a quarter thick. e f g h, Another of the same size and thickness, but of an octagon shape, ik, A cylinder 4 in. long. which connects the above two together, leaving a round hole at the top, of half an inch wide. Im, A movable core 24 inches long, covered top and bottom; it is to be put into i k. o, The screw about 14 in. long or more.

P, A square knob fastened to the screw o.

q, A cork with a circular hole on one side.

r, A collet of a vine, a little longer than the cork 4, and to be placed within it.

st are the same as qr, but now supposed to be placed in the hole of a b cd. They are to be pushed down, leaving ta little above the surface, which is to be cut off with a flat-bladed razor. Then carefully turn the screw an eighth round, which will raise the collet sufficiently to enable you with the razor to take off a thin slice.

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