684 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 

 of the Phanerogamia. 



a. Anatomy. 

 (1) Cell-Structure and Protoplasm. 



Cytological Investigations.* — Herr B. Nemec finds that in the 

 periblem of the root-tips of Allium Gepa, before the appearance of the 

 hyaline periblast, the threads of the polar radiation are differentiated 

 in a collection of dense protoplasm at the two poles of the nucleus. 

 The threads radiate towards the equator of the cell. 



From a great number of observations the author derives the conclu- 

 sion that the form and the polar disposition of the chromatin loops in 

 the spirem are dependent on the arrangement of the nuclear network. 



In the nuclear division in the root-tip of the alder, the nucleole 

 diminishes in size during the prophase, then places itself in the equatorial 

 plane, and becomes constricted into two halves, each of which moves 

 towards one of the poles, and there vanishes. The two daughter- 

 nucleoles have a perfectly free motion, and are not in contact with any 

 achromatic threads. 



In the nuclear division in the root-tips of Equisetum arvense no hyaline 

 periblast exists up to the time of the dissolution of the nuclear wall. 



The author does not believe in the existence of centrosomes or 

 similar structures in the vegetative cells of vascular plants. The part 

 played by the centrosome where it does exist is in them played by the 

 entire nucleus. 



Amitotic Division of the Nucleus.! — Herr A. Nathansohn has 

 followed out the observations of Gerasimoff on the influence of cold on 

 the division of the nucleus, by experiments on the action of ether 

 (a 1 p.c. aqueous solution) ; the objects being Spirogyra, Closterium, 

 the root-cells of flowering plants, &c. Similar results were obtained. 

 The constriction of the nucleus is preceded by that of the nucleole 

 where there is only one ; if there are two nucleoles, the nucleus is first 

 constricted, then the nucleoles in the two daughter-nuclei. No perfect 

 transition between mitotic and amitotic division Avas observed. Amitotic 

 division of the nucleus can therefore be produced artificially, and may 

 proceed as far as the production of perfect daughter-cells. 



Karyokinesis in the Pollen-mother-cells of Liliacese.J — The results 

 of observations on this subject made by M. V. Gregoire in the case of 

 Lilium 8pecio8um, L. candidum, L. croceum, and Fritillaria imperialis, 

 lead him to different conclusions from those of Weismann. He states 

 that the ball divides at first longitudinally into two halves interlacing 

 with one another, and subsequently transversely into twelve distinct 



* 



Fiinfstiick's Beitrage, iv. p. 37. See Bot. Ztg., lviii. (1900) 2'" Abt., p. 206. 

 t Pringsheim's Jahrb. f. wiss. Bot., xxxv. (1900) pp. 48-79 (2 pis.). 

 X La Cellule, xvi. (1899) pp. 233-98 (2 pis.). 



