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"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 18 of a millimetre in the Potato, and the To 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: Svo; 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 chlorophyll, 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

by him in the Annales des Sciences, n. s. x. 319. t. 3., from Marchantia polymorpha, Chara vulgaris, Sphagnum acutifolium, and Hypnum triquetrum.

Page 295.

M. Payen, in a second memoir upon this subject, names the unchanged primitive tissue of plants cellulose, and says it has the same composition as starch; the matter of lignification he regards as the true lignine of chemists. (Comptes rendus, viii. 52.)

Page 344.

The observations by Mr. Griffith on Indian Loranthaceae have been continued by M. Decaisne upon the common Mistletoe ; and he finds that, although that plant flowers in the months of March and April, the ovule does not make its appearance earlier than the end of the month of May, or the commencement of June. (Comptes rendus, viii. 202.)

Page 347.

All these statements have now been copiously illustrated by excellent figures in Schleiden's memoir Ueber Bildung des Eichens, und Entstehung des Embryos bei den Phanerogamen.

Page 368.

There are some secondary forms under which nutritive matter is provided for plants, the most important of which is starch. The purpose which nature intends this almost universally diffused substance to answer, in the system of vegetation, is essentially nutritive. It is formed in plants soon after their parts become organised, and it collects there till in some instances, such as albumen, tubers, rhizomata, and the cellular part of endogenous stems, it forms the principal part of the mass. In such cases it is ready to be chemically changed at a fitting period, and to become the food of the germinating embryo, or of young stems and leaves. According to M. Payen, it is enabled to execute this important purpose, by virtue of its gradual solution by water and diastase, which convert it into dextrine and sugar, and thus render it capable of percolating the surrounding tissue, and passing from chamber to chamber of parenchyma. (Mémoire sur l'Amidon, p. 131.)

Page 351.

According to Payen (Comptes rendus, viii. 60.), those manures are the most efficient which are richest in nitrogen, for he considers that plants are generally able to obtain, in most cultivated soils, a sufficient supply of the other principles necessary to their existence, without the addition of manure. But this does not quite agree with an assertion of Boussingault, that although some plants rob the air of a considerable quantity of nitrogen, yet others do not assimilate it at all. (Ib. 55.)

Page 380.

Mr. Rigg has investigated the connection between nitrogen and plants, the results of his enquiries being given in the Philosophical Transactions for 1838, p. 395. &c. He finds the youngest parts of plants richest in nitrogen, the germ of Peas and Beans containing by weight about 200 parts of that gas for 1000 parts of carbon, while the cotyledons contain only from about 100 to 140 parts. He is disposed to believe that those seeds of the same kind, which contain the largest quantity of nitrogen, germinate the earliest. Alburnum he finds to contain more nitrogen than duramen, and fast-growing timber more than slow-growing, whence he infers that nitrogen exercises its influence in causing decomposition. The latter opinions he considers to be rendered still more probable by the proportion of nitrogen found in different species of wood, cæteris paribus: thus in satin wood and Malabar teak, both timber of great durability, the quantity of nitrogen is almost inappreciable; in Dantzic and English oak, the quantity is also very small; in American birch which soon decomposes, nitrogen is found in large quantities. Mr. Rigg finds nitrogen in large quantities in Vine leaves when they first make their appearance: as they are developed it decreases in proportional quantity; is in excess during the period of most rapid growth, and towards the close of the year it is comparatively small. He states the full-blown petals of the Rose to contain 24 parts of nitrogen in 1000 of carbon, while the unexpanded and central petals contain 66 parts.

In another paper also published in the Philosophical Transactions for 1838, p. 403., Mr. Rigg has considered the evolution of nitrogen during the growth of plants, and the sources from which they derive that element. He states that his enquiries all tend to prove that nitrogen is evolved during the healthy performance of the functions of plants; that the proportion which it bears

to the oxygen given off is influenced by the sun's rays; but that owing to the necessary exclusion of the external atmosphere during the progress of experiments, it is impossible, with any degree of accuracy, to calculate the volume of these evolved gases during any period of the growth of plants in their natural state. If to this indefinite quantity of nitrogen given off by plants, there be added that definite volume incorporated into their substance, the question arises, whence do plants derive their nitrogen, and does any part of it proceed from the atmosphere? This problem Mr. Rigg has endeavoured to solve by a series of tabulated experiments upon seeds and seedling plants, the result of which is a large excess of nitrogen in the latter, and under such circumstances of growth that he is compelled to fix upon the atmosphere as its source. He has also arrived at the conclusion, that the differences which we find in the germination of seeds and the growth of plants in the shade and sunshine, are due in a great measure to the influence of nitrogen.

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