1918] DISEASES OF PLANTS. 451 



Various factors favorable to infection were noted, among them inmiaturity 

 and imperfect curing of the bulbs ; the application of commercial fertilizers 

 late in the season or in incorrect proportions; the application of large quanti- 

 ties of stable manure before planting ; poor air drainage in the field ; and high 

 humidity, high temperature, and poor ventilation in the storage house. 



Methods of control have been worked out which include field sanitation, 

 care of the curing crop, and storing in properly constructed and regulated 

 houses. Fumigation of the stock with formaldehyde gas just before or just 

 after storing has been found ineffective against the fungus. While spraying 

 the growing crop with Bordeaux mixture has given some promising results, 

 this method of treatment has not been tested sufllciently to warrant definite 

 recommendations. 



A bibliography is appended. 



Onion neck-rot in storage houses, F. H. Hall {Neio York State Sta. Bui. 437, 

 popular C(L {1911), pp. S, figs. 3). — A popular edition of the above. 



Early blight of potato and related plants, R. D. Rands (Wisconsin Sta. Re- 

 search Bid. 1^2 {1911), pp. ^iS, figs. 10). — The history, occurrence, and economic 

 importance of early blight of potatoes and related plants due to Altcrnaria 

 solani are given, together with stu<lies on the host range of the fungus and its 

 morphology, physiology, and life history. 



The disease, which is said to be practically world-wide, causes premature 

 death of the foliage and thus indirectly damages the crop. In Wisconsin, the 

 fungus is known to occur on the potato, tomato, and eggplant, the species pre- 

 viously reported on the jimson weed being a different form to which the author 

 has given the name A. crassa. 



Early blight is said ordinarily to make little development until the host 

 plant has passed its period of greatest vigor and is being weakened by external 

 conditions or the drain of tuber formation. Climate and ^il were found to 

 exert a controlling influence on the disease, and the conclusion is reached that 

 the development of early blight requires relatively high temperatures alternat- 

 ing with moist periods, in combination with a more or less weakened condition 

 of the plant. 



Crop rotation and the destruction of dead potato tops, together with spray- 

 ing with Bordeaux mixture, are recommended for the control of the disease. 



Study of a bacterial disease of soy bean and the nature of the root nodules 

 of Glycine soja and Arachis hypogtea, P. C. van der Wolk {Cultura, 2S {1916), 

 Nos. 336, pp. 26S-2So; 337, pp. 300-319). — Besides a discussion of parasitic and 

 so-called symbiotic relationships, the author gives an account, with his explana- 

 tions, of a soy-bean disease which, appearing first as an etiolated condition, 

 may result in the death of the plant. The trouble appeared to be due to the 

 activities of the bacterium {Ehizobixmi bcyerincJcii) associated with the root 

 nodules, which are here compared with plant galls. 



In health, the nodule maintains close relationship with the leguminous plant 

 by means of outgrowths suggestive of the haustoria of some parasitic plants. 

 Detached nodules, no matter how small, kept in nutritive media but not those 

 kept in water, acted somewhat as individual organisms, attaining a considerably 

 larger size than those naturally attached. The normal and the abnormal 

 processes, as well as the forms and structures which occur in the rootlets, are 

 described in some detail, as is also the behavior of these outgrowths in healthy 

 and in diseased plants. 



The trouble appears to be connected primarily with the lowering of re- 

 sistance and decrease of protective products in the single layer of cells lying 

 between the nodule and the rootlet proper and normally acting as an absorbing 

 organ and also a barrier to these bacteria and fui-nishing an antidote for their 



