ZOOLOGY VXD l'.OTAXV, .MICROSCOPY, ETC. 685 



Alternation of Generations in Myxomycetes.* — V. Vouk has con- 

 sidered the Myxomycetes from a biological and cytological standpoint. 

 He concludes that the zoospores are the vegetative stage or progameto- 

 phyte ; the nryxauioebae, also a vegetative stage, and the plasmodium or 

 generative stage, belong to the gametophyte generation. The fruiting 

 body with spores, the fructiricative stage, corresponds to the sporophyte. 

 He calls the first generation a water-form, the second a land-form, of 

 life. 



New Research on Plasmodiophoracese.t — Rene Maire and Adrien 

 Tison have made further studies of Sorosphaera Veronicse, and of Tetra- 

 myxa parasitica, which they also include among the Plasmodiophoracete. 

 It forms tumours on Ruppia rostellata. A series of forms that do not 

 form tumours have been described by them under the genus Ligniera. 

 The parasite of TrigJochin, Tetramyxa triglochinis, is constantly asporo- 

 genous, and has been placed in a new genus Molliardia. Schizogonic 

 mitosis is remarkably similar in all the known Plasmodiophoraceae, and 

 the absence of multiple karyogamy before spore-formation thus separates 

 the family from the Myxomycetes. The affinity of Ligniera with Rhizo- 

 myxa and Woronina suggests the origin of Plasmodiophoraceae as near 

 to the Chytridiales. 



Spongospora subterranea.^ — T. G. B. Osborn has written an account 

 of the life-history and cytology of this parasite of the potato. It 

 lives in the cells of the tuber in an amoeboid condition, and invades the 

 new cells as they are formed in the tissue. The nuclei of the amoebse 

 divide amitotically, and then fuse to form a plasmodium. This is fol- 

 lowed by degeneration, and the vegetative nuclei are replaced by chro- 

 midia — the akaryote stage. Following this, the nuclei are formed on 

 different sites from the previous ones, some chromidia being used in the 

 process while the remainder degenerate. Karyogamy takes place between 

 pairs of nuclei, after which the enlarged nuclei show contraction of the 

 chromatin, possibly a condition of synapsis. Two karyokinetic divisions 

 of the nucleus follow, the second having eight chromosomes. The spores 

 are uninucleate, and are massed into spore-balls. Spongospora is a 

 member of the Plasmodiophoraceae. 



Life-history of Sorosphaera graminis.§ — E. J. Schwartz found this 

 new species on tubercles on the roots of grasses. The swellings were 

 caused by eel-worms ; the second parasite was an amoeboid organism, 

 which proved to be a Sorosphaera. The grasses were partially affected 

 by the presence of the tubercles : they were less healthy and less frequently 

 in flower. Schwartz describes carefully cytology and development of 

 the species. It is closely allied to S. Junci and S. Veronicas, and does 

 not materially differ from them in its life-history. 



* Oesterr. Bot. Zeitschr., lxi. (1911) pp. 131-9. See also Bot. Centralbl., cxvii. 

 {1911) p. 33. 



t Ann. Mvcol., ix. (1911) pp. 226-46 (5 pis.). 

 I Ann. of "Bot., xxv. (1911) pp. 327-41 (1 pi.). 

 § Ann. of Bot., xxv. (1911) pp. 791-7 (1 pi. ). 



Oct. 18th, 1911 -2 v 



