ZOOLOGY A.ND BOTANY, MICROSCOPY, ETC. 475 



BOTANY. 



A. GENERAL, including Embryology and Histology 

 of the Phanerogamia. 



Structure of Protoplasm and of the Cell-nucleus.* — F. Sclimitz 

 has aj)plied to the examination of vegetable protoplasm the mode 

 adopted in animal histology, of hardening and afterwards colouring, by 

 which the finer structure can be detected, as already described by 

 Frommann.f 



The protoplasmic body consists of a reticulated framework of 

 extremely fine fibrillse, varying much in their development. Even in 

 the youngest meristem-cells the protoplasm is not uniformly dense ; 

 the peripheral layers are finely dotted, while towards the middle are 

 larger or smaller homogeneous lacunee, bounded by finely dotted 

 plates, bands, or very delicate threads of protoplasm, the number 

 of the lacuna continually increasing with the age of the cells. Sub- 

 sequently they increase also in size, and frequently coalesce with one 

 another, until finally the protoplasm is reduced to a parietal utricle, 

 with a larger or smaller number of bands or threads crossing the 

 cell-cavity. The thicker bands and the parietal layer clearly mani- 

 fest the reticulated structure. Imbedded in the protoplasm are almost 

 always small strongly refractive granules, which assume a darker 

 tincture — the " microsomes " of Hanstein, which the author regards 

 not as metaplasmic enclosures, but as essential constituents of the 

 protoplasmic body itself. The intermediate substance between the 

 meshes of the fibrillar framework is a homogeneous fluid. The sepa- 

 rate meshes are in open communication with one another. When 

 a large central vacuole has been formed, the adjacent innermost layers 

 of the fibrillar network often form a special darker bounding-layer, in 

 consequence of becoming closely applied to one another. In those 

 cells the membrane of which has undergone a partial thickening 

 in the form of spiral or reticulate ridges, as well as in those numerous 

 cases where the cells, when old, completely lose their protoplasm, the 

 protoplasmic utricle is at first always thinner, is detached with greater 

 difficulty from the cell- walls by contracting reagents, until at length 

 only isolated portions and the nucleus remain, the latter being fixmly 

 attached to the cell- wall ; the substance of the protoplasmic utricle is 

 gradually used up in the thickening of the cell-wall. The framework 

 of fine fibrin^ does not consist of rigid immotile fibres, but of a 

 living motile protoplasm, which is continually undergoing change of 

 form. 



The cell-nucleus consists of a matrix, in which, after hardening 

 and colouring, a very fine punctation can be recognized, probably due 

 (as in the protoplasm generally) to a similar reticulate structure. 

 The nucleus is often bounded on the outside by a special layer, in the 



* SB. Niederrhein. Ges. Natur. u. Heilkunde, Bonn, 1880. See Bot. Centralbl. 

 i. (1880) p. 1294. 



t See this Journal, iii. (1880) p. 823. 



