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PHYSIOLOGICAL BOTANY.

lopment of cells. The investigations exhibit a depth ofresearch, which commences with the very earliest originof the plant, and in this respect they are very valuable.First, Mohl, to whom we are indebted for most of ourknowledge on this point, has published :

Remarks on the Structure of the Vegetable Cell, in theBotanische Zeitung. Edited by H. von Mohl and L.von Schlechtendal. Berlin , 1844, p. 15 et seq., andp. 273 et seq.—He was led to these researches byHartig’s investigations upon the structure of cells, andhis assumption of their possessing a more internal mem-brane which lines their interior, and which he deno-minated a Ptychode. “ If we examine a first year’sshoot of a tree, or the stem of an annual plant, which,before the completion of its growth, has been immersedin spirit and kept in it for some time, we find in allthose cells and vessels, the secondary layers of whichhave not yet attained their full development, an innermembrane, which is remarkably distinct from the othermembranes of the cell. This membrane forms a per-fectly closed, cell-like, thin-walled vesicle, which in thefresh plant is closely applied to the inner wall of the cell,and therefore escapes observation; whilst in specimenswhich have been preserved in spirit, it is contracted, andmore or less detached from the wall of the cell.” Hecalls this cell-like vesicle the primordial utricle, and foundit in a number of Dicotyledonous plants, as, e. g, inSambucus ebulus, Ficus carica , Pirns sglvestris, AsclepiasSgriaca, Hoya carnosa, Euphorbia Canariensis, CaputMedusa, &c. In the Monocotyledons, he detected it inthe apex of the stem and of the root. But this utriclecan be seen by a shorter method than that of keepingthe portions of the plants for a long time in spirit. Ingeneral, the preparation need only be exposed to theaction of nitric or hydrochloric acid for a few minutes ; ifthe acid be then neutralized with ammonia, and the pre-paration be coloured by iodine, the primordial utricle is