DISEASES OF PLANTS. 227 



After the iiourisbraeiit in the phuit is exhausted the zoospoiangia 

 become cysted, taking ou a very thick dark brown and slightly spiny 

 wall. The cysts are less spherical and ordinarily are smaller than the 

 sporangia. In this state the parasite can endure extremes of drought 

 and cold and thus perpetuates itself from year to year. 



From the nature of the mycelium, method of formation of zoospo- 

 rangia, form and dehiscence of zoosporangia, coexistence of zoosporan- 

 gia and cysts the author determined the fungus as an undescribed 

 genus of Chi/trkliacew, to which he gives the name I'l/roctoniiDi sphcu- 

 ricum. 



The author states that this is the first time a member of this group 

 has been reported as attacking field crops so as to cause serious loss. 

 Without doubt the abundant rains of the spring aided very greatly in 

 its growth, but under ordinary weather conditions a fungus capable of 

 such extensive and rapid spreading will prove destructive. 



The burning of the stubble and occasional rotation should be 

 employed in infested regions. Straw and litter from the wheat should 

 not be used as manure, as the cysts will be carried over uninjured. 

 Seed wheat from infested regions should not be used, as it, too, may 

 carry the cysts. 



Potato scab, L. 11. Taft and K. J. Coeyell {Michigan ISta. Bui. 

 108, pp. 38-15, figs. 3). 



Synopsis. — Report of successful tests of corrosive sublimate and Bordeaux mixture 

 for the prevention of potato scab. Corrosive sublimate solution, 1 part to 1,000 

 or 1 to 2,000, gave most decisive results. 



The authors carried on investigations for the purpose of finding the 

 best strength and the proper time for soaking the seed to prevent potato 

 scab. In treating with corrosive sul)limate three strengths were used — 

 1 part of corrosive sublimate to 750 parts of water, 1 part to 1,000, and 

 1 j)art to 2,000. The soil where the potatoes were planted Avas of a 

 very uniform clay loam which had been cropped with garden vege- 

 tables for about .20 years and received an annual dressing of compost 

 for most of the time. No potatoes had been grown upon it for 6 years. 



No definite information was gained from the treatment where the 

 stronger solution was used, except that it was fairly successful in pre- 

 venting the scab and that the seed treated a long time was slower in 

 sprouting. With the weaker solutions — 1 part to 1 ,000 and 1 part to 

 2,000 — practically the same results were obtained. The scab decreased 

 as the length of treatment increased, as did also, within certain limits, 

 the yield. 



