ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 597 



locality and conditions of growth of the hosts. The form of the galls 

 corresponds more or less to these divisions, and may be reckoned as of 

 specific character. Rytz gives a long account of other species, also 

 describing the development and cytology of the different stages in their 

 life-history. The paper is well illustrated, 



Chytridiaceae.* — J. Le Serbinow^ has made a special study of the 

 genera in this natural order of fungi. He gives an historical account of 

 them in the first part of his paper ; in the second part, he recounts his 

 own observations of their growth and development, and describes the 

 different forms he has examined. He distinguishes three new^ genera ; 

 Catenaria, Sporophlyctes, and Saccomyces. The new forms are well 

 illustrated. 



Mildew of Spinach.f — R. Laubert examined the Peronospora that 

 infests spinach and Ghenopodiam, supposed to be P. effusa. He found 

 that there were morphological differences that separated the two fungi, 

 and he makes a new species, P. Spinacke. The spores of the latter are 

 larger and the sporophores are more sparingly branched. Mildew on 

 spinach has never become an epidemic : only a few plants in a bed as a 

 rule show the disease, as large yellowish spots on the leaves. 



Formation of Abnormally Large Cells in Mucor.J — G. Ritter has 

 been experimenting on the influence o-n the growth of fungi of certain 

 media, chiefly acids. He found a tendency to produce giant cells, 

 especially in Mucor spitiosus, when grown in a sugar solution with a 

 definite addition of inorganic ammonia salts and a small percentage of 

 organic acids. Ritter gives the quantities used by him that were most 

 effective in bringing about this result. He suggests possible explana- 

 tions of the phenomenon, but arrives at no definite conclusion. 



Heterothallism in Rhizopus nigricans.§ — Two papers' have appeared 

 recently in which the heterothallic nature of this mould is questioned or 

 denied. The authors claimed to have produced zygospores on hyphs 

 'arising from a single spore. A. F. Blakeslee * replies to the two writers 

 in restating his own findings and in giving growth results obtained by 

 him on material sent by Namyslowski, one of the authors in question. 

 He restates his previous finding, that where zygospores are formed, there 

 must be two strains, and where opposite results seem to have been 

 ■obtained, the culture must have been impure. 



Blakeslee || also contributes a paper based on his work on Mucor to 

 a discussion as to the biological significance and control of sex. He 

 reviews the theories held by scientific workei-s on this' subject, but he 

 concludes that a further accumulation of facts is necessary before we are 

 in a position to determine what, if any, unifying principle there may be 

 in the wide-spread phenomenon of sexuality. 



European Discomycetes.^ — Emile Boudier has published a volume 

 containing the history and classification of the Discomycetes. He cites 



* Script. Bot. Hort. Univ. Imp. Petrop., xxiv. (1907) pp. 5-173 (6 pis.), 

 t Gartenflora, svi. (1906) p. 17. See also Bot. Centralbl., cv. (1907) p. 25. 

 X Ber. Deutsch. Bol. GeselL, xsv. (1907) pp. 255-66 (1 pi.). 

 § Bot. Gazette, xliii. (1907) pp. 415-18. 

 II Science, n.s., sxv. (1907) pp. 366-72. 

 ^ Histoire et Classification de Discomycetes d' Europe, Paris ; Paul Klinck- 

 sieck, 1907, vii. and 221 pp. 



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