GOO SUMMARY OF CUHRENT researches RELATma TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 



of the Phanerogamia. 



a. Anatomy.* 



Q) Cell-structTire and Protoplasm. 



Division of the Nucleus, Cell-division, and Impregnation.!— Prof. 

 E. Strasbiugcr has coutiuued his observations ou the changes ■which take 

 place during the division of the nucleus in vegetable and animal cells. 

 He adopts Schwarz's terminology of linine for the sxibstance of the 

 hyaloplasmic filaments of the nucleus in a state of repose, chroviatine for 

 the substance of the granulations. The filaments of linine are composed 

 of numerous folds, and anastomose so frequently in the nucleus when in 

 a state of repose, that it presents the appearance of a weft of close 

 meshes in which the threads cannot possibly be followed throughout 

 their course. The nuclear cavity does not, however, as the author 

 previously supposed, contain only a single filament. The use of eau do 

 Javelle shows that the division of the nucleus is not accompanied by the 

 segmentation of a single filament, but by the dissociation of filaments 

 ali-eady distinct. 



The filaments of the spindle are always formed, in the higher plants, 

 at the expense of the cytoplasm which has penetrated into the nuclear 

 cavity, as has been shown also by Guignard. The changes which take 

 place in the nuclear filaments, as well as the movements which they per- 

 form, are of an active nature, and the poles serve only to regulate this 

 movement. The movements which the filaments execute in the knot-phase 

 ("phase du peloton") are independent of the future poles, showing that 

 the filaments are endowed with forces of their own, capable of modifying 

 their structure and of changing their position. While this phenomenon 

 is proceeding, the nuclear membrane is still intact. The two poles of 

 the future spindle are formed in the surrounding cytoplasm during the 

 phase of lax knot. After the formation of the bundle and of the nuclear 

 plate, the segments double themselves where they have not done so 

 previously. The secondary segments of each daughter-nucleus approach 

 onc-auother, and the surrounding cytoplasm envelopes them with a 

 membrane ; no other elements take part in the formation of the daughter- 

 nuclei. 



There can be no doubt that, in the higher plants, the cytoplasm 

 enters into the nuclear cavity for the purpose of forming the spindle- 

 fibres. The spindle filaments do not persist in the form of primary con- 

 necting threads between the secondary segments; and it is only at a 

 later period that they receive an addition of secondary filaments at the 

 expense of the cytoplasm entering between their interstices. The whole 

 mass of filaments usually separates later from the daughter-nuclei, and 

 forms between them a lenticular body surrounded by the cytojilasm. 

 "When the cells are filled with cell-sap, the cytoplasm finally forms 

 around the connecting filaments only a tube with more or less thin wall, 



* This subdivision contains (1) Cell-sti-ucture and Protoplasm; (2) Other Cell- 

 contents (including Secretions); (3) Structure of Tissues; and (4) Structure of 

 Organs. t Morot's Joum. Bot., ii. (1888) pp. 81-91. 



