508 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nuclear Evolution in Ascomycetes.* — A. Gruilliermond reviews the 

 whole history of nuclear discovery in the Ascomycetes, giving special 

 attention to work done on Humaria rutilans, Peziza catinus, Pustularia 

 vesiculosa, and Qalactinia succosa, with an account of his own observations 

 and work on these forms. He concludes that the number of chromosomes 

 is constant in the three divisions of the spore nucleus of the ascus, and 

 he therefore dismisses the theory of a second reduction during spore- 

 formation. 



Mildew of the Vine in Poland.f — J. Brzezinski states that the 

 vine is not frequently cultivated in Poland on a large scale, though 

 there are vines in most private gardens. Oidium Tuckeri has occurred 

 only occasionally up to the present, and generally on plants recently im- 

 ported. The author, however, records an outbreak of the mildew which 

 re- appeared three successive years. He found also the perithecia of 

 Uncinula americana, the perfect fruit form, but only in more sheltered 

 positions. In the autumn of 1910, which was exceptionally cold, no 

 specimen of Uncinula could be found. The parasite, however, had been 

 so far acclimatized as to persist during three successive seasons. 



Oak-mildew.} — Paul Magnus discusses the question as to the 

 affinities of this mildew. He decides that the Oidium belongs to the 

 genus Mkrosphsera. The Pyrennsean oak Quercus Tozza was the first 

 and the most severely attacked from western France down to Morocco, 

 and he argues that a Mkrosphsera allied to M. Alni has attacked the 

 oak as a new host, and so far has only formed oidia. Other cases of 

 such transference from host to host are quoted. The American tree 

 Quercus rubra remained untouched by the fungus side by side with 

 European oaks that were attacked. 



Pythium de Baryanum.§ — L. Peters found this fungus attacking 

 seedlings of Pelargonium, both before and after the roots were formed. 

 The plants are most liable to be attacked in heavy damp soil. Spinach 

 plants were also attacked by the same fungus, and the stems blackened 

 at the base. The fungus was either Pythium de Baryanum or one nearly 

 allied. 



Monochytrium, a New Genus of the Chytridiales.|| — R. F. Griggs 

 found the new fungus on the ragweed, Ambrosia artemisifolia. It 

 inhabits the cells of the host, usually epidermal or hypodermal, but 

 causes very little hypertrophy. It is difficult to find and is not abundant. 

 Monochytrium is distinguished by the binucleate sexual resting-spores 

 and the solitary zoosporangia. A detailed account of the development 

 and cytology of the fungus is given so far as has been observed. 



Helvella crispa.lf — D. Carruthers has followed the development of 

 ascus and spores in Helvellee, and gives an account of her observations. 



* Rev. Gen. Bot , xxiii. (1911) pp. 89-120 (2 pis.). 



t Bull. Int. Acad. Sci. Cracovie, 1911, pp. 1-6. 



% Ver. Ges. Luxemburg Naturfr., 1910, pp. 108-111. See also Centralbl. Bakt., 

 xxx. (1911) p. 114. 



§ Gartenflora, lix. (1910) p. 209. See also Centralbl. Bakt., xxix. (1911) pp. 

 115-6. || Obio Naturalist, x. (1911) pp. 44-54 (2 pis.). 



^ Ann. Bot., xxv. (1911) pp. 244-52 (2 pis ). 



