drawing fig. 3., at bede) will be seen precipitating into the latter solution sundry beautiful distinct blue specks. This precipitate or blue colour arises from the union of the prussiate of potash, which had ascended from the cup by those vessels, and now discharges itself into the sulphate of iron. You may easily see the difference of the two precipitates that of the liber will be black, from the causes already mentioned, whilst that on the vessels of the alburnum will be a deep blue. Again, with a sharp clean knife, cut a collet in a longitudinal direction; then apply the sulphate of iron, and immediately will be seen the blue precipitate in the same sort of vessels, but of considerable length; and by carefully cutting the alburnum lengthwise, they may be seen an inch long, or upwards.

The continuation of these ascending vessels might be discovered in the stalk, and also in the leaf of the vine, by the blue precipitate, were it not for the gallic acid of the liber, from its black precipitate blending immediately with the Prussian blue, so that the two sets of vessels cannot be distinguished from each other. However, recourse may be had to others; either the shoot of an apple tree, which contains no gallic acid, or to some of the cabbage tribe, which I prefer, from their leaves being smooth and broad. Therefore, place some large cabbage or broccoli leaves, or even a cabbage plant run to seed cut off a little above the ground, in a cup, with the solution of the prussiate of potash, for 36 hours. On cutting their stalks across, or any part of their leaves, in any direction, and applying the sulphate of iron, the ascending sap-vessels, by the blue precipitate, will be immediately seen in them. Afterwards, it may be a satisfaction to apply the sulphate of iron to some leaves that have not been prepared with the solution of the prussiate of potash; but no precipitate will be discovered, thus showing the absence of gallic acid. If some of the cabbages, &c., be left three or four days in the solution, the vessels of the cellular texture will be seen most beantifully, when cut through, by applying to them the sulphate of iron. If one experiment be more gratifying than another, it is seeing the ramification of those minute vessels, not only conspicuously in the stem, the stalk, and the leaf, but more so in the medulla.

I think it is very evident (reasoning by analogy) that, had it not been for the precipitate formed by the gallic acid, the ascent of the prussiate of potash would have been traced in the ascending vessels of the stalks, and also in the leaves, of the vine. The ascending vessels may be clearly seen, by the above process, in the flower of the white lily, and also in the fruits of the peach, pear, and apple, provided they are left on the branches; but not so well in the currant, raspberry, or straw

berry, owing to their cellular and horizontal vessels, as well as their liber containing an abundance of gallic acid, which would cause the precipitates, as before mentioned, to blend together.

Some of the ascending sap-vessels of the vine are remarkably large an individual one might be traced from near the point of a root to within a short distance of the claw, as I shall term it (for the six together resemble the claws of a bird, and the idea is strengthened by the stalk of the leaf resembling its leg); see fig. 2. at e f g h i k, which represent the six claws, and the stalk or leg at m. These vessels become much smaller near the claw; and, on entering it, they are extremely fine, so that the finest hair cannot be passed down them, but which might have been easily done to any other except those six.

On looking at the alburnum, one would suppose the ascending sap-vessels in drawing fig. 4., from q to r, marked h h, and in fig. 3., b c d e, were formed merely by leaving small circular holes during its growth; but on minutely examining them with a powerful microscope, it will be discovered that each hole contains a vessel within, of a remarkably fine, silvery, paper-like texture, which possesses the power of protruding the sap forward, as will be more fully illustrated hereafter.

I am well aware of the interesting theory of the vital motion, &c. &c., by Monsieur Dutrochet, mentioned in Vol. III. p. 78., and more fully in No. I. of The Foreign Quarterly Review, p. 78.; but I consider that every vegetable action arises from a vital principle inherent in itself, and not from the attraction of heavy fluids, even when confined in a membrane or sac, for others of lighter specific gravities, which that gentleman calls endosmose; and exosmose when lighter fluids pass outwards through such membrane or sac into heavy fluids ; but that this vessel, or lining of the alburnum, possesses an animated power to protrude the sap forward. The following experiment will more clearly exemplify my meaning: - Cut off an inch or two from the middle of a collet of a vine, and, after making both ends very smooth with a sharp clean knife, moisten the upper end a very little with the solution of the sulphate of iron; afterwards, put a few drops of the prussiate of potash on the concave side of a watch-glass, and then place therein the other end of the collet; in a few minutes the upper end will become spotted with blue, from the prussiate of potash having ascended up those vessels and precipitated the sulphate of iron on the upper surface. Now, as no leaves, joints, or roots of the vine were attached to the collet, nothing but its own vital principle could have raised the solution. Some may think the union of the divisions by lateral pressure might produce the ascent: this is easily proved to be incorrect; for, on

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 d d, 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 e e. 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 klm.

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 e f 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 a 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 gh. 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 no 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 ƒ ƒ 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