ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 475 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 

 of the Phanerogamia. 



a. Anatomy. 

 (1) Cell-Structure and Protoplasm. 



Energids and Cells.* — Sig. R. Pirotta reverts to Hanstein's idea of 

 the protoplast as a general fundamental conception. Protoplasts may 

 carry on an independent existence, or may combine — " monoplasts " or 

 " polyplasts." Monoplasts may be devoid of membrane, and may then 

 be termed gymnoplasts, or may be invested witb a membrane, and are 

 then dermoplasts. Gymnoplasts may be uninucleate (monokaric) or 

 multinucleate (polykaric) ; and the same may be the case with dermo- 

 plasts (Peronosporaceae, Saprolegniaceae, idioblasts, &c). In the Schizo- 

 phyta there is no sharp differentiation between cytoplasm and nucleus. 

 In polyplasts the union may be such that the separate protoplasts re- 

 main distinct, and they may then be termed meriplasts ; when the poly- 

 plasts are so completely fused together that their cytoplasms form a 

 single mass in which a number of nuclei are imbedded, Hanstein's term 

 " symplasts " may be applied. When the union of the meriplasts is only 

 temporary, the individuality of the protoplasts not being disturbed, they 

 form a " protoplast-colony " or " energid-colony " (Goebel) ; such colonies 

 may be formed either of gymnoplasts or of dermoplasts. Symplasts may 

 also be either gymnosymplasts, such as plasmodes, or dermosymplasts, as 

 latex-vessels. 



Position and Function of the Nucleus.f — Pursuing his researches 

 on the formation of non-nucleated cells, Herr J. J. Gerassimoff states 

 that if the cells of Spirogyra are subjected to a more or less considerable 

 cooling during division, daughter-cells may be obtained containing no 

 nucleus. The tendency to a symmetrical arrangement of the cell-con- 

 tents in Spirogyra depends on two constant forces — the action on one- 

 another of the nucleus and of the other cell-contents, and the action on 

 one-another of the nuclei themselves. The function of the nucleus may 

 be regarded as the transmission to the other cell-contents of an energy 

 generated in itself, comparable to the electric energy. 



Reduction- division, Spindle - formation, Centrosomes, and Ble- 

 pharoplasts.J — The following is chiefly extracted from Prof. C. J. 

 Chamberlain's review of this important work by Prof. E. Strasburger. 



In agreement with Guignard and Gregoire, but in opposition to 

 Belajeff and Weismann, Prof. Strasburger maiutains that in the forma- 

 tion of spores from spore-mother-cells, the splitting of the chromosomes 

 is, in both the nuclear divisions, longitudinal ; there is, therefore, no 

 reducing division. In the formation of the pollen-mother -cells, he reverts 



* Riv. Sci. Biol., 1899, fasc. 3, 14 pp. See Bot. Cetitralbl., lxxxii. (1900) p. 116. 



t Bull. Soc. Imp. Moscou, 1899 (1900) pp. 220-67 (35 figs.). Cf. this Journal, 

 1897, p. 134. 



% • Ueb. Reductionstheiluug, Spindelbildung, Centrosomes, u. Cilienbildner im 

 Pflanzenreich,' Jena, 1900, xx. aud 224 pp. aud 4 pis. See Bot. Gazette, xxix. 

 (1900) p. 145. 



