662 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including- Cell-Contents. 



Observations on Reduction-division.* — Strasburger has published 

 a short account of his present views on this division and the for- 

 mation of the reduced number of the chromosomes. He states that 

 when the network of the microspore-mother-cell of Tholictrum pur- 

 purascens has collected at one side of the nucleus, the chromatin 

 separates from the linin threads and forms a number of granules. These 

 then collect round a number of centres corresponding to the number of 

 the future chromosomes, in this case twelve. These centres he terras 

 gamocentra. The granules then form definite bodies at these points, in 

 which they are with difficulty to be individualised. These bodies then 

 become stretched out somewhat, and clearly divided in the middle ; the 

 individual granules of the two halves then separate into two portions, 

 and with the help of the linin become arranged in threads. A single 

 continuous thread is thus formed, and the synapsis stage is over. The 

 longitudinal splitting of the thread then follows. 



Recent Work on Cytology. f — M. Koernicke gives a very useful 

 account of all the more important botanical work on the protoplasm and 

 nucleus published during the last few years. 



Heterotypic Division.:}: — J. Bergbs has studied this division from 

 the spireme stage onwards, in the development of the microspores of 

 Allium and Lilium. He agrees neither with Dixon nor with Farmer and 

 Moore as to the origin of the chromosomes, but believes that they are 

 produced from the spireme thread by mere shortening and thickening, 

 and that the two halves of the chromosome are produced by longitudinal 

 splitting. 



Function of the Nucleolus.§ — H. Wager has studied nuclear division 

 and the relation of the nucleolus to the process of karyokinesis in the 

 root apex of Phaseolus. He concludes that the nucleolus contains 

 chromatin more or less combined with plastin ; and that the chromatin 

 passes into the chromosomes. Further evidence in support of this view 

 is supplied by a study of the reconstruction of the daughter-nuclei, 

 towards the formation of the nucleoli of which the chromatin contributes. 

 The author considers that the nucleolus is possibly concerned with the 



* SB. K. Akad. Wiss. Berlin, xviii. (1904) pp. 587-615 (9 figs, in text), 



t Ber. Deutsch. Bot. Gesell., xxi. (1904) Generalversaniml.-Heft, pp. 66-134. 



% La Cellule, xxi. (1904) pp. 171-86, pi. 1. 



§ Aim. Bot., xviii. (1904) pp. 29-55 (1 pi.) 



