82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fungi. 



. Fertilisation in the Saprolegnieae.* — A. H. Trow has published 

 further observations on the cytology and fertilisation of Achlya polyandry 

 and A. De Baryana. He goes over the whole group, noting the point. -i 

 that have been successfully investigated by various workers, and re- 

 affirms the correctness of his own conclusions as to fertilisation in 

 certain members of this family. He finds in Achyla polyandra that at 

 an early stage of the oosphere after " balling " has taken place only one 

 nucleus is present, at a later stage two nuclei, and still later again one. 

 He has observed again and again the order 1-2-1, which of itself, he 

 holds, proves the process of fertilisation of the oosphere. Further, he 

 found and figured a fertilisation tube in open communication with the 

 oosphere. He made similar observations in A. De Baryana. In the 

 oogonium and antheridium of this species, on first formation, there are 

 a number of nuclei which undergo a first and second mitosis. During 

 the latter division the chromosomes are reduced from eight to four, and 

 centrosomes and astrospheres are observed for the first time in the 

 oogonial nuclei. " Balling " of the different oospheres takes place after 

 the degeneration of the supernumerary nuclei, and the oospheres seem 

 to be uninucleate until the entrance of the male nucleus from the ferti- 

 lisation tube of the antheridium. The male nucleus acquires a centro- 

 some and astrosphere after passing into the oosphere. During maturation 

 of the oospore the wall thickens and granules of reserve-material collect 

 in the protoplasm. At this stage fusion of the two nuclei takes place, 

 centrosomes and astrospheres having disappeared from both nuclei. 

 Here, as in A. polyandra, Trow finds the recurrence of the formula 

 1-2-1, indicating the succession of nuclei, and again proving fusion 

 and consequently fertilisation. 



Studies on the Fertilisation of Albugo Lepigoni and some 

 Peronosporeae.t — W. Ruhland finds that Albugo Lepigoni is the species 

 of the genus in which there is the greatest reduction of nuclei, as only 

 one of the originally large number passes from the periplasm to the 

 oosphere. In the other species there is copulation between a number 

 of male and female nuclei, or, where one alone persists, there are at 

 first a large number in the oosphere. This phenomenon bespeaks a 

 close connection between A. Lepigoni and other Peronosporeas, although 

 the formation of chained conidia marks a wide difference between the 

 genera. 



Vegetable Pathology 4 —Under this title G. Cuboni gives an 

 account of a disease of wheat caused by Sclerospora macrospora. This 

 fungus has been included among the Peronosporeas, but according to 

 the observations of Cuboni and others, the hyphas are intra-cellular, they 

 never form haustoria, and they never produce conidiophores. The 

 author tried in every possible way to induce the growth of conidio- 

 phores, without success. The wheat is invariably attacked after an 



* Ann. Bot., xviii. (1904) pp. 541-69 (3 pis.). 



t Jalub. wiss. Bot... xxxix. (1904) p. 135. See also Bot. (entralbl., xcvi. (1904) 

 p. 340-1. + Atti Reale Accad. Lincei, ccci. (1904) pp. 5K-7. 



