ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 285 



author has made exact studies of the conidia and oospores, of their 

 growth and germination. He finds that the walls of the hyphas, conidia 

 and sexual organs are largely, though not entirely, composed of cellu- 

 lose ; the walls of the oogonium and oospore consists of two different 

 layers. The conidia germinate either by producing germ-tubes direct 

 or by the formation of zoospores. The zoospores germinate after a 

 resting period. The first change is the dissolution of the thick inner 

 portion of the wall which has apparently served as a reserve of carbo- 

 hydrate food material. These sexual organs occur in the underground 

 stalks and rhizomes, and in one case were found in a potato tuber. The 

 name suggested for the disease is Pink-rot wilt ; it is evidently con- 

 tracted from the soil, and is of serious consequence in land which has 

 borne a crop of potatoes for several successive seasons. 



Development and Treatment of Mildew.* — H. Faes collected and 

 preserved, during the winter season, leaves of the vine which contained 

 abundant oospores of Plasmopara viticoJa. Some of these he kept dry in 

 the laboratory and some on moist soil in a cold chamber. Attempts to 

 inoculate the vine with this material in the following spring were with- 

 out result, and the author thinks that even in the open field germination 

 of oospores occurs but rarely. Other infection experiments with the 

 mildew were carried out on buds and fruit. In the former case it was 

 found very easy to infect the flower buds, but when the grapes had 

 reached the size of peas, the skin was already impervious, and only the 

 stalk took the disease. 



A. Istvanffi f also records results of infection experiments with the 

 vine mildew. As to the time required for penetration by the swarm- 

 spores and the consequent formation of oil-spots, he found that in the 

 beginning of June twelve to fourteen days were required, but with the 

 advance of summer, shorter time was required, though in the beginning 

 of July owing to the thickness of the grape skin twelve to fourteen days 

 was again recorded as the period necessary before the fungus took effect. 

 In excessive moisture, in the laboratory, development was more rapid. 



Germination of Teleutospores.J— It is well-known that the teleuto- 

 spores — the resting spores — of rusts will not as a rule germinate unless 

 they have passed the winter in the open and have been exposed to the 

 changes of weather. Klebahn has made a special study of the conditions 

 that prevent or induce germination, and now gives his results. He finds 

 that recurrent moistening of the spores with fresh water is an important 

 factor, more especially when it alternates with complete drying. Such 

 conditions are encountered in ordinary weather changes. In a warm 

 room these conditions can be imitated and germination even hastened by 

 2-3 months, as compared witli germination in ordinary circumstances. 

 Drying up is not absolutely essential, as spores on material kept con- 

 tinuously in water developed promycelium and sporidia in about the 



* Rev. Vitic, xxxix. (1913) v. 161. See also Centralbl. Bakt., xl. (1914) pp. 

 322-3. 



t Bot. Kozlem., xvi. (1913) pp. 1-7. See also Centralbl. Bakt., xl. (1914) pp. 

 323-4. \ Zeitschr. Pflanzenkr., xxiv. (1914) pp. 1-32 (23 figs.). 



