ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 505 



BOTANY. 



GENERAL, 

 Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including- Cell-Contents. 



Behaviour of the Chromosomes in the Spore-Mother-Cells of 

 Higher Plants.*— D. M. Mottier has studied nuclear division in the pollen- 

 mother-cells of Lilium Martagon, L. candidum, Podophyllum peltatum, 

 and Tradescantia virginica, and those of the corresponding divisions in 

 the embryo-sac mother-cell of Lilium Martagon. The details of the suc- 

 cessive phases are described in detail. " The first mitosis in both the 

 micro- and macrospore mother-cells of the higher plants is heterotypic, 

 and the second homotypic. These nuclear divisions are not, properly 

 speaking, reducing or reduction divisions. They are not the agents of 

 the reduction, but rather the result of the numerical reduction of the 

 chromosomes." Cytological evidence favours the view that the niicro- 

 and macrospore mother-cells are homologous. That type of the embryo- 

 sac in which four potential macrospores are produced as the result of the 

 heterotypic and homotypic mitoses, occurring in Gymnospernis as well as 

 in the majority of Angiosperms, is regarded as the more primitive, while 

 that typified by Lilium, where the macrospore mother-cell functions at 

 once as the spore, is to be regarded as a derived condition. 



Reconstitution and Formation of Chromosomes in Somatic 

 Nuclei .f — Gregoire and Wygaerts publish a preliminary account of their 

 observations on the minute details of nucleus reconstitution, and the 

 formation of the chromosomes in somatic cells, chiefly meristematic. 

 The authors believe that the resting nucleus is derived from the chromo- 

 somes, not by their fusion end to end, but by a gradual process of 

 alveolisation ; but in the objects studied the chromosomes retain their 

 individuality even in repose. The chromosomes are formed again by a 

 process exactly opposite to that by which the resting nucleus was formed ; 

 they contain no discs or granulations so that when the chromosome 

 splits it simply separates directly into halves. 



Behaviour of the Chromosomes of Hybrids.! — 0. Rosenberg has 

 investigated the behaviour of the hybrid Drosera longifolia x rotundi- 

 folia which is found in nature near Tromso. The number of chromo- 

 somes in I), rotundifolia is 20 (not 16 as stated earlier by him) in the 

 sporophyte and 10 in the oophyte, while in D. longifolia the number is 

 40 and 20 respectively, just twice as many. In all the vegetative cells 

 of the hybrid ?>() chromosomes were found (except in the tapetal cells 

 where a few nuclei with about 40 chromosomes were observed). The 

 spindle figure was somewhat broader than that of D. rotundifolia, but 



* Bot. Gazette, xxxv. (1903) pp. 250-82 (4 pis.), 

 t Beih. z. Bot. Centralbl., xiv. (1903) pp. 13-19. 

 j Ber. Deutsch. Bot. Ges., xxi. (1903) pp. 110-8 (1 pi.). 



