978 SUMMARY OF CUllUENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 

 of the Phanerogamia. 



a. Anatomy.* 



Q) Cell-structure and Protoplasm. 



Division of the Nucleus and of the Cell. — Prof. E. Strasburgcrt 

 follows out Lis previous importaut observations on this subject with 

 aclditioual ones, among which the following are the more important 



points : — 



(1) Division of the nucleus and of the cell in Spirogyva polyt^niata n.sp. 

 As respects the development of the spindle-fibres, this occupies an inter- 

 mediate position between species already described. 



(2) The resting nucleus. In that of Fritillana, there arc no bridges 

 which are less receptive to pigments between the thicker strings of the 

 framework of the nucleus, as Flcraming and others have described in the 

 case of Salamandra. 



(3) Construction of the nuclear threads in the knot-condition. The 

 relatively large chromatin-discs of the nuclear thread during karyokinesis 

 are the result of gradual fusion of the usually much smaller chromatin- 

 balls in the framework of the resting nucleus. 



(4) Number of the nuclear threads. Contrary to his previous view, 

 Strasburger has now, in preparations fixed in alcohol, and stained by 

 methyl-blue, and afterwards treated with eau de Javelle, demonstrated 

 the segmentation of the nuclear thread in the resting nucleus. In the 

 vegetative organs he found sometimes slight variations in the number 

 of segments during karyokinesis, while in tlic nuclei of generative cells 

 the number appears to be very constant. It seems probable that the 

 number of segments in the threads of the two nuclei which unite in the 

 process of impregnation is always the same in the higher plants. 



(5) The loose knot-condition of the polar field. Strasburger shows 

 that the formation of the segments of the nuclear filaments in the direc- 

 tion of the so-called polar field, first observed by Eabl in animal cells, 

 occurs also in various vegetable cells. He now agrees with Guignard 

 and Zacharias in regarding the structures which he had previously 

 described under the name paranucleoli as identical with the nucleoli 

 of the nucleus. 



(6) Transformation of the nuclear filaments in the formation of the 

 nuclear plate. The author shows that in various vegetable cells the polar 

 field formed at the commencement of the knot-stage lies in the equatorial 

 plane of the figure in the subsequent division of the nucleus. 



(7) Origin of the nuclear spindle and formation of the nuclear plate. 

 The polar corpuscles found in animal cells have not been detected in 

 those of plants. Eadial structures in the cytoplasm are, however, not 

 altogether wanting during karyokinesis. The processes which take place 



* This subdivisiou contains (1) Cell-structure and Protoplasm; (2) Other Cell- 

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

 Organs. 



+ ' Ueb. Kern- u. Zell-theilung Im Pflanzenreiclie, nebst eiuem Anhang iib. 

 Befruchtung,' 258 pp., Jena, 1888. Sec Bot. Centralbl., xxxv. (1888) p. 192. See 

 also Nature xxxix. (1888) p. 4. Cf. this Journal, 1883, p. 227. 



