"Size. The acicular vary exceedingly in their measurement, some being not more than Too part of an inch in length, whilst others will be as much as . The conglomerate form is not subject to so much variation, varying only from to part of an inch. The size of the rhombohedral and other forms of crystals has no uniformity as to measurement, some being not more than 2, whilst others are the part of an inch.

"Composition. According to Raspail, the composition of the acicular and conglomerate forms differs, the former being phosphate, whilst the latter are oxalate of lime. Unger mentions that Buchner, Nees von Esenbeck, and others, have found that their bases are sometimes lime, magnesia, and silica, the latter not often occurring; and that these bases are united to carbonic, oxalic, and phosphoric acids. The whole of these assertions are more or less correct, but Raspail has only given us negative proofs of their composition. It is not difficult to obtain positive ones, by the following experiments : —

"If Raphides of the conglomerate form (perfectly free from cellular tissue) be heated red hot, it will be observed that they at first become black and again white, as the heating is continued to redness in this state they readily dissolve in weak nitric or hydrochloric acid, with effervescence; if to this solution oxalate of ammonia be added, a copious white precipitate is obtained, which indicates that the base in this case has been lime. In detecting the acid united with the lime, the proceeding is a little more complicated. For this purpose the crystals are to be dissolved in dilute nitric acid, which occurs without effervescence; to this solution nitrate of silver is to be added, when a heavy white precipitate is produced, which, when washed with distilled water to free it from any excess of acid and nitrate of silver, is to be dried; if after this a small portion be heated in the flame of a lamp it explodes, by which it is proved that the precipitate is oxalate of silver. These results, which may be performed with certainty with conglomerate Raphides, plainly proves their composition to be oxalate of lime.

"The acicular can be demonstrated to be phosphate of lime, by proceeding thus. If heated red hot, they do not dissolve in acids with effervescence, a fact which essentially distinguishes the composition of the two kinds. When dissolved in dilute nitric acid, if oxalate of ammonia be added, we have the characteristic precipitate of lime; if with a portion of the acid solution be mixed a little nitrate of silver, a white precipitate is not obtained, as in the last case, but one of a lemon colour, which is such as denotes the

combination with silver of phosphoric acid, which must have been furnished by the acicular Raphides.

"Though phosphoric and oxalic acids united with lime are found the most frequent components of these minute crystals, there can be no doubt that tartaric acid enters into their formation in certain plants, as in the fruit of the Grape, where the crystals are found of a different figure from those in the interior of the leaves or stem; and also that magnesia can be frequently detected combined with lime, and perhaps never forms crystals with acid, without lime entering also into their composition.

"Silica, though it frequently forms an organised part of vegetables, seldom exists as crystals in their interior. In a bark from Para, which is said to be manufactured into a kind of pottery, silica exists in abundance in granular fragments, which, however, do not put on a crystalline form.

"Conclusion.-It is not known what purposes these bodies fulfil in the economy of plants, but it has been conjectured, since amylaceous matters are deposited, and again appropriated for the support of the carbonaceous portion of the tissue, according to the necessities of the individual, that these crystals may be deposits to be applied towards the mineral part or skeleton of the plant, as occasion may require: but it has been found from experiments that these calcareous bodies are insoluble in vegetable acids, and the silica of course in every thing; consequently they cannot be taken up again, are therefore unsuited to the vital exigencies of the vegetable, and probably are of no use, even mechanically, in the several tissues which contain them, because plants of many kinds do not secrete such formations: therefore, it will be nearer the truth to regard them, as Link has done, as nothing more than accidental deposits.

"In all the analyses lime has been found the greatest constituent of these bodies and since this material is so intimately associated both with animal and vegetable organisation, as not perhaps to be wanting in any individual of either kingdom, there is every reason for its being so generally the base of such crystals. Moreover, since it is the property of some vegetables to combine, out of their materials of sustenance, varied proportions of oxygen and carbon, which, when apportioned in the ratio of three of the former to two of the latter, form oxalic acid, the presence of that agent in a plant, in contact with lime, can scarcely fail in producing a crystalline substance with it. Again, as phosphoric acid is a frequent accompaniment of animal and vegetable organisation either

introduced with the food, or created out of it, (it being yet a problem to solve how this and other elementary matters are produced,) it can be readily conceived why compounds with it and lime should be formed as well as with the former acid; because, as the earthy and other matters are absorbed from the moisture of the soil, they must necessarily meet with these acids when they exist, and the vitality of the plant does not prevent their forming the crystals which have been here described; still there are some curious points connected with their production. If oxalic or phosphoric acid be added to a solution of lime, instead of crystals, a pulverulent opaque precipitate is obtained, which does not happen in the interior of the plants: therefore various experiments have been devised, to discover the method of making crystals by combining the above substances. Some have been ineffectual, such as making a plant, which contains lime in its composition, absorb water with a small quantity of oxalate of ammonia dissolved in it from the want of temperature which would create a necessity for moisture in the plant this experiment failed. A method, however, which succeeded was, to connect a vessel containing a solution of oxalate of ammonia with one containing lime water, by means of a few fibres of cotton: this gradual introduction of one fluid to the other formed perfect crystals of oxalate of lime on the ends of the fibres which were in contact with the lime water. This having succeeded, another attempt was made to form them in the interior of the cells of such plants as did not previously possess them: some difficulty occurred in finding any one fitted for the purpose, and at last Rice-paper, as it is termed, (the concentric slice from the pith of Eschynomene and Hibiscus,) was selected as the best material for the experiment, from its admitting an examination of their formation, by becoming transparent when charged with fluid.

"This substance was placed in lime water under an air pump, and the cells were soon filled with that fluid; it was then dried and submitted two or three times to the same process: by this means the cells were well charged with lime. Portions of this substance were placed in weak solutions of oxalic and phosphoric acids, and allowed to remain. On the third day, when examined, the cells in both instances contained much precipitate, together with numerous crystals; those in the oxalic acid being precisely like the conglomerate form in Rhubarb, and those in the phosphoric being rhombohedra, but none of the acicular shape were found, even after continuing the process beyond eight or ten days.

"These experiments distinctly prove the origin of Raphides, which appear to be compounds that become crystallised merely by the slow admixture of their constituents, and are probably modified by gummy, amylaceous, and other matters which are contained in the juices of the plant. Their formation does not seem confined

to living structures or to any particular tissues or organs of a plant; but the process may be carried on in any situation, as can be proved in the Grape vine, in which crystals can be discovered in every organ, and in the vascular as well as in the cellular tissue."

Page 44.

In addition to the observations of Fritzsche upon the organisation of starch, M. Payen has lately published an elaborate memoir upon the same subject. He finds the granules varying in size between the 185 of a millimetre in the Potato, and the Too of a millimetre in the seed of Chenopodium Quinoa. When crowded within the cells that generate them they become polyedral, but if floating in a thin fluid their common character is to be rounded. They are composed of successive thin layers, formed over each other, round a hilum or point of attachment to the wall of a cell: the matter of which they consist is of a uniform nature, and is formed by addition to the interior into which it penetrates through the hilum, the external layers being the oldest and toughest, and often thickened by being coated with other matter, such as vegetable mucus, calcareous salts, a fixed oily matter, and essential oil; this additional matter is what has given rise to the opinion that grains of starch have a peculiar integument. Amylaceous matter may be found in all the organs of plants, under favourable circumstances, except in their nascent state; the spongioles, very young leaf buds or flower buds, and the interior of the unimpregnated ovule are always destitute of starch. M. Payen has not found it in vessels or in intercellular passages, nor in the epidermis, and it is generally absent in the strata of immediately subjacent parenchyma. It is in the more interior parts, removed from the direct action of air and light, that it is principally met with, and especially in roots and underground forms of stem. (Mémoire sur l'Amidon: 8vo; Paris, 1839.)

Page 46.

In the tubercular roots of terrestrial Ophrydeæ, such as those which form the salep of the shops, I have shown that there

are large cells filled with a matter as clear as water, and apparently of the nature of bassorin; and that this bassorin-like principle is composed of minute cells, each with its cytoblast, so compactly aggregated in the interior of the parent cell, that from this circumstance, and from their very equal refracting power, they form an apparently homogeneous mass.

Page 58.

Mohl has examined the stomates of Hyacinthus orientalis in their progress of developement. He finds them in their earliest stage a single quadrangular cell, rather broader than long, and either empty or filled with green molecular matter. In the next stage, this single cell is cut in two by a partition which is directed across the smaller diameter, and separates the molecular mass into two equal parts. At a third stage, the angles round off, and the partition is seen to be double, with an opening in its middle. Later still, the molecular mass is broken up into granules of chlo rophyll, the original cell is become oblong, the passage through the double partition has acquired its full size, and the stomate is complete. (Linnæa, xii. 544. t. 5.)

Page 210.

In a valuab.e paper upon the successive formation of the parts constituting the fructification of Leguminosa, the authors, Messrs. Schleiden and Vogel, have clearly shown that in that case the carpellary leaf is originally a folded scale, and that when the ovules appear it is from the margins of that leaf, and not from the central point of the axis; so that it seems clear that the latter must be considered the origin of ovules only in certain instances. (Beiträge zur Entwickelungs-geschichte der Blüthentheile bei den Leguminosen.)

Page 220.

The observations made by Mr. Griffith upon the ovule of Loranthacea and Santalum have been followed by others on the part of M. Decaisne, who finds that in Thesium the structure of the ovule is of the same nature as that of Santalum. (Comptes rendus, viii. 203.)

Page 270.

The spermatic animalcules mentioned by Meyen are figured