620 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Development of the Sexual Organs of Vaucheria.* — W. Heidinger 

 gives an account of the development of the sexual organs in \'inirlicrin, 

 as studied in species representing the four groups — CorniculataB Bessiles, 

 Corniculatse racemosse, Anomalae, Woroninia. He contrasts the respec- 

 tive statements (1) of Oltmanns, that before the oogonium becomes 

 walled off, all the nuclei hut one are withdrawn into the pedicel, and 

 (2) of Davis, that after the oogonium is walled off, all the nuclei but 

 one undergo degeneration and disappear. After describing his own 

 methods of investigation, lie gives a detailed account of the develop- 

 ment of the sexual organs of V. pachyderma, V. arrhyncha sp. n., 

 V.terrestris, V. geminata, and Woroninia dichotoma. He then criticises 

 B. M. Davis's work ; adds some systematic notes ; and sums up his 

 results by stating that they confirm Oltmanns' view, and that in all the 

 groups of Vaucheria examined the multinucleate rudiment becomes a 

 uninucleate oogonium by the withdrawal of all the other nuclei into 

 the pedicel just before the oogonium is cut off by the transverse wall. 

 The proper nucleus remains in the apex of the oogonium and puts out 

 processes into the surrounding plasma, but moves back into the centre 

 just before fertilisation, and remains there until germination of the 

 oospore. 



Spore-formation in Derbesia.f — B. M. Davis gives an account of 

 the formation of the zoospores of Derbesia Lamourouxu. These are 

 large and not biciliate, as in other Siphonales, but provided with a circle 

 of numerous long cilia at the forward end. The lateral globular out- 

 growth, which develops into a sporangium, becomes separated from the 

 parent filament by the closure of the ingrowing annular thickening in 

 the neck. The sporangium contains at first thousands of nuclei, all alike, 

 slightly larger than the plastids, and each containing a small nucleolus 

 and a large chromatin body. Some of the nuclei enlarge to a diameter 

 4-6 times that of the plastids, and are rendered conspicuous by the 

 development of numerous protoplasmic strands radiating out from the 

 cytoplasm enveloping the nucleus. These large nuclei are the centres of 

 the future spores. The other nuclei do not fuse (as has been stated), but 

 undergo degeneration. The spore-masses separate and become rounded 

 up. The nuclei of each moves from the centre towards the periphery, 

 and a circlet of granules is deposited, by means of the protoplasm strands, 

 under the plasma-membrane near by. It does not arise from the plasma- 

 membrane. This circlet is the blepharoplast, which splits into two rings ; 

 from the lower ring the circle of cilia is produced. The homogeneous 

 chromatin becomes changed into an irregular network of coiled threads. 

 The two rings of the blepharoplast remain for a time at the base of the 

 germinating spore, then gradually grow fainter. The nucleus divides 

 mitotically, the spindle being intranuclear. 



West Indian Species of Avrainvillea.J — F. Borgesen publishes an 

 account of the species of Avrainvillea hitherto found on the shores of 

 the Danish West Indies, based upon material collected there by himself 



* Ber. Deutsch. Bot. Gesell., xxvi. (1908) pp. 313-63 (1 pi. and figs.). 



+ Ann. of Bot., xxii. (1908) pp. 1-20 (2 pis.). 



X Vidensk. Meddel. Natur. Poren. Kjobenhavn, 1908, pp. 27-44 (1 pi., figs.). 



