332 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including- Cell-Contents. 



Blepharoplast and Centrosome of Marchantia polymorpha.* — 

 End. Escoyez has studied the so-called centrosomes which occur in the 

 spermatic mitoses of Marchantia polymorpha, and finds that these bodies 

 only occur in the last division, and that while in form and position they 

 resemble true centrosomes, their real function is that of blepharoplasts. 

 They are, in fact, organs sui generis, and the relation between them and 

 the spindle can be simply explained by the special mode of division of 

 the mother-cell of the sperrnatozoids. 



Nucleus and Karyokinesis in Zygnema.f — The same author has in- 

 vestigated karyokinesis in Zygn&ma, and draws the following conclusions 

 from his observations. All the chromosomes are produced from a 

 chromatic network ; the nucleolus only provides chromatic material for 

 the chromosomes, but contributes no morphological elements. The 

 chromosomes are elongated rods which split longitudinally in the usual 

 way ; this is seen most clearly in the metaphase. In the telophase, the 

 chromosomes, which are at first crowded together, spread out into the 

 nuclear vacuole, and are united by their drawn-out ends. The nucleolus 

 is formed at this stage, not from the united chromosomes, but quite 

 independently from the chromatic network. The chromosomes appear 

 to retain their individuality from one mitosis to another. The pyrenoids 

 and chromatophores multiply by simple fission, independently of the 

 nucleus. 



Nuclear Structures in Synchytrium.J — F. L. Stevens has described 

 some unusual nuclear figures from the large nucleus of Synchytrium 

 decipiens. One of these is a nucleus without a membrane, consisting 

 wholly of chromatin and a large nucleolus ; this form appeared always 

 in cells with one nucleus, and therefore before any division had taken 

 place. Other phenomena noted were the asters variously connected with 

 nuclei, and evidently of extranuclear origin ; but the absence of a 

 complete series of figures made it impossible to identify the different 

 stages, and so to explain the nature of the various bodies seen. The 

 development of the resting spore is followed, and of the sporangia. 



Peroxydiastase in Dry Seeds.§ — Brocq-Rousseu and E. Gain have 

 experimented with seeds of different ages obtained from plants of 



* La Cellule, xxiv. (1907) pp. 247-54 (1 pi.). 

 t Tom. cit., pp. 354-64 (1 pi.). 

 % Ann. Mycol., v. (1907) pp. 480-4 (1 pi.). 

 § Comptes Rendus, cxlv. (1907) pp.' 1297-8. 



