242 SUMMARY OF CURRENT RESEARCHES RELATING TO 



*' Brown Rot " Diseases of Fruit-trees, with special Reference to 

 two Biologic Forms of Monilia cinerea. II. — H. Wormald {Ann. Bot., 

 1920, 34, 143-71, 2 pis.). The author has established the existence in 

 Britain of two species of Monilia, viz. 31. fructigena, the conidial stage of 

 Sclerotinia fructigena, and M, cinerea. The former causes a fruit rot 

 of apples, plums and cherries, and on apple-trees produces cankers by 

 invading the branch through the fruit. M. cinerea causes " blossom 

 wilt" and "canker disease " on apples; the same on plums, with, in 

 addition, a " wither tip " of young shoots ; while on cherry-trees it gives 

 rise to " fruit rot," " blossom wilt " and " twig disease." 31. cinerea 

 produces conidia from December onwards which are smaller than the 

 summer forms. 31. fructigena forms no conidia in winter. Various 

 biological peculiarities are also described. A complete bibliography is 

 appended. A. L. S. 



Physiological Study of the Parasitism of Pythium debaryanum 

 on the Potato Tuber. — L. A. Hawkins and R. B. Harvey {Journ. 

 Agric. Res., 1919, 18, 275-97, 2 figs.). The authors experimented with 

 a number of potatoes ; they found that while some were very susceptible, 

 others, such as the White McCormick, were resistant to the disease. 

 They think it probable that the fungus penetrates the epidermis of the 

 potato by puncture rather than by enzymes, and they explain the 

 immunity of the McCormick tubers by the condition of its cell walls. 

 The rate of growth of the fungus in the McCormick is also much 

 slower. A. L. S. 



Biology of Fomes applanatus. — J. H. White {Trans. Rog. Can. 

 Inst. Toronto, 1919, 133-74, 6 pis.). The fungus attacks practically all 

 deciduous trees and several conifers, causing great damage to timber. 

 The author describes the basidiospores as : " Yellow papillate thick-walled 

 chlamydospores within a thin hyaline wall." A. L. S. 



Plant Sanitation in Fruit Plantations. — F. T. Brooks {Trans. 

 Brit. 3Iycol. Sec, 1920, 6, 253-62). The author lays down certain 

 principles that should be attended to if disease is to be eradicated from 

 orchard, garden, field or forest. It is most important that no harbourage 

 for the disease should be left. Discarded and dead branches should be 

 removed ; dead or mummified fruits should be destroyed ; in the case of 

 rusts the alternative hosts should be eliminated. Sanitation measures 

 such as spraying, cultivation of the soil, etc., should be directed by 

 experts with knowledge of the diseases and of the local conditions. The 

 author is convinced that by careful control measures such baffling 

 diseases as silver-leaf can be overcome ; its presence is often clue to great 

 neglect. A. L. S. 



Notes on some Diseases of Aspen.— Carl Hartley and Glen G. 

 Hahn {Phytopatkologg, 1920, 10, 141-7, 3 figs.). PopuJus trenmloidesl 

 a widely distributed American forest tree, is unusually subject to disease. 

 The authors have investigated there and report : — Leaves are killed by 

 Sclerotium bifrons, and rusted by 3IeIa7npsora alberlensis ; Fomes 

 igniarius causes premature death in the stems, while other minute fungi 

 attack injured portions. A. L. S. 



