660 abstracts: phytopathology 



to the intimate relationships between Oryzomys and Nectomys, and 

 other American cricetines, and incidentally expresses the opinion that 

 Nesoryzomys, based by Heller on rice rats inhabiting the Galapagos 

 Islands, is a synonym of Oryzomys. 



Keys to the forms; lists of specimens examined, with footnote refer- 

 ence to the museums where the material from various localities may be 

 found; average and extreme dimensions of specimens; detailed distri- 

 bution of each form; and, in the plates, nearly 100 well-selected figures 

 of skulls and teeth; all add to the values of the revision, which is based 

 on the examination of 1613 specimens assembled from the various 

 larger American museums, N. Hollister. 



PHYTOPATHOLOGY. — Seed treatment control and overwintering of 

 cucumber angular leaf spot. W. W. Gilbert and M. W. Gardner. 

 Phytopathology 8:229-233. May, 1918. 



The authors give the results secured from small and large scale tests 

 of disinfecting cucumber seed to control angular leaf spot. The treat- 

 ments tried consisted in soaking the seed for 5 to 10 minutes in solutions 

 of mercuric chlorid (1 to 1000), copper sulfate (0.5 and 1 per cent), 

 and formalin (2 and 4 per cent) and then washing in running water. 

 Hot water treatment (52°C. for 10 minutes) was also tried. Half-acre 

 field tests carried on at Madison, Wisconsin, showed conclusively that 

 all the treatments tried almost entirely eliminated the disease from the 

 seed. The mercuric chlorid treatment (1 to 1000 for 5 minutes) is 

 considered the safest, most practical, and most effective method tested. 

 Both formalin and copper sulfate caused some injury to germination. 

 The effectiveness of the treatment with mercuric chlorid was further 

 tested on about 150 cucumber fields in Wisconsin and Indiana, in one 

 half of which the seed used was treated and in the remainder untreated. 

 The original seed was from the same source. Observations made near 

 the end of the season showed a very considerable reduction in the 

 amount of disease on fields not previously in cucumbers planted with 

 treated seed. The data secured on overwintering indicate that the dis- 

 ease does live over in the soil to a considerable extent, making it inad- 

 visable to plant cucumbers on the same land two years in succession. 



Seed disinfection and crop rotation are advised as methods of con- 

 trolling angular leaf spot. W. W. G. 



