ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 341 



Phytophthora and Plasmopora in Ohio.* — Phytophthora infestans, 

 the deadly potato disease, is rare in Ohio. A. D. Selby has examined 

 into the climatic conditions that have determined its appearance in 

 Ohio and elsewhere. He suggests that, as the potato is a native of cool 

 regions, it is evident that the parasite will also be favoured by the same 

 weather conditions as the host. A succession of cool seasons in Ohio 

 would give opportunity to the fungus to spread into the country, and a 

 cycle of hot or dry seasons would again stamp it out. 



Plasmopora cubensis is a sub-tropical species first recorded from 

 Cuba. It has done much damage to garden cucumbers and squashes. 

 It makes its appearance in Ohio earlier in a warm season than a cold 

 one. It survives the winter in Florida, and each season it seems to 

 advance northward with the warmer weather. 



Zygospores of Rhizopus nigricans.f — Boleslas Xamyslowski found 

 that two plants were included under R. nigricans, the one origin- 

 ally described by Ehrenberg as R. nigricans, the other, cultivated at 

 Utrecht, which he names R. nodosus. It was found that the latter pro- 

 duced only sporangia in all circumstances, while from the former in 

 suitable conditions zygospores could also be produced. The structure 

 and development of the zygospores has been followed and described. 

 They contain a large number of nuclei of varying size, but no copulation 

 was observed, and the role of these nuclei has not been determined. 

 The author contests A. Blakeslee's theory as to the heteroecious nature 

 of this fungus. He grew plants from one spore and obtained from the 

 culture a plentiful growth of zygospores. The condition necessary to 

 induce the formation of zygospores is a suitable medium, which was 

 found in bread soaked in grape-sugar, or in slices of petir. He never 

 obtained the spores on bouillon, peptonised water, potatoes, gelatin, 

 bouillon-jelly or beer-must. In addition, the air must be saturated with 

 humidity, but not too moist. When it is supersaturated all development 

 ceases. If the air is dry, sporangia only are produced. Namyslowski is 

 of opinion that Blakeslee, in the case of this fungus, had sometimes a 

 mixture in the culture, and where no zygospores were produced, the 

 reason was to be sought in the culture medium rather than in the nature 

 of the plant. 



Morphology of the Ascocarp, and Spore-formation in the Many- 

 spored Asci of Thecotheus Pelletieri. % — This minute fungus, a 

 member of the Ascobolese, has been investigated by James Bertram 

 Overton. He gives a resume of all the literature bearing on the 

 different points touched on by him in his examination of the fungus, 

 and then recounts results of his own observations, which he sums up 

 thus : (1) The fruit-body of Thecotheus is formed from several asco- 

 gonia, and is, therefore, a compound apothecium. The ascogonia are 

 multinucleate, some containing as many as a dozen nuclei. (2) The 

 ascogenous hypha arise from any or all of the cells of the ascogonium, 

 and, consequently, the cells of the ascogonium are not connected by 



* Ohio Naturalist, vii. (1907) pp. 79-85. 



t Bull. Acad. Sci. Cracovie, Classe Sci. Math.-Nat., 190G, pp. 676-92 (1 pi. and 

 12 figs ). t Bot. Gazette, xlii. (1906) ^jp. 450-92 (2 pis.). 



