244 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Moulding of Snow-smothered Nursery Stock. — Carl Hartley, 

 Roy G. Pierce and Glenn G. Hahn {Phytopathology, 1919, 9, 

 521-31). The authors state that evergreens smothered by tight pack- 

 ing or by snow covering are liable to injury from parasitic fungi attacking 

 the leaves. Botrytis cinerea and a dark sterile mould unidentified are 

 the most prevalent causes of trouble. The best way found to treat the 

 disease is to sprinkle black soil on the snow early in spring to hasten the 

 melting. Nurseries for raising Douglas fir should not be established 

 where there are prolonged winter conditions. A. L. S. 



Fungal Diseases of the Common Larch. — W. E. Hiley {Oxford, 



1919, 204 pp., 73 figs.). The fungi dealt with in the book are in the 

 following order, which is also the order of importance : — Canker due to 

 Dasyscypha calycina ; heart-rot caused by Fomes annosiis ; heart-rot 

 less frequently caused by Polyporus Schiveinitzii, Porta vaporaria, 

 Polyporus sulphiirens and Torametes Pini ; disease due to Armillan'a 

 mellea ; and finally leaf and seedling diseases, the former being attacked 

 by Sjjhderella laricma, Meria laricis, Hypodermella laricis, Melampsoridium 

 betulmum, Melampsora tremidse, and the latter liable to suffer from 

 damping off due to Phytophthora omnivora and Fusoma parasiticum. 

 The list of diseases is, as observed by the author, rather depressing 

 reading, but the fungi are not all equally virulent or equally common. 

 Full descriptions are given of them all and of damage that results to the 

 tissues from their presence. In a general summary at the end there is 

 advice given as to the selection of soil for larch planting, so that the 

 roots of the trees may be well aerated. The canker of the larch is 

 possibly the most to be feared, as the fungus causing it is very wide 

 spread ; but Ar miliar ia mellea does also much harm and is equally 

 abundant, and is not confined to larch. There is a good bibliography 

 and a full index. A. L. S. 



White Rot Disease of Onion Bulbs. — A. D. Cotton {Journ. Agric, 



1920, 26, 1093-9, 3 figs.). The fungus causing the disease appears as 

 a fine fluffy mycehum on the onions, which became attacked in the soil 

 at the end of May or early in June, the visible symptoms of the disease 

 being the wilting and yellowing of the foliage. At a further stage 

 minute black sclerotia about the size of a poppy seed are formed in great 

 numbers, and by August the plants are mostly killed. The sclerotia 

 drop back into the soil where they pass the winter. In spring the 

 sclerotium germinates directly, forming hyph^ which infect new onion 

 plants. The name Sclerotium cepivorum was given by Berkley to the 

 fungus in 1841, and has been retained as it never shows any Sclerotinia 

 stage. No success has followed the use of soil fungicides, and the best 

 way of combating the disease is to starve out the fungus by changing the 

 crop for a number of years — eiglit or ten may not be too long. A. L. S. 



Leaflets on Plant Diseases. — Ministry of Agriculture and 

 Fisheries (Publications Branch, 3 St. James's Square, London, S.AV.l). 

 A series of these leaflets have recently been revised and re-written, 

 and may be had free of charge from the Publications Branch. They 



