62 a EXPERIMENT STATION. [Jan. 



with extreme humidity. Such conditions promoted rapid, but 

 soft and tender, growth. In consequence the dehcate young 

 needles of many trees were burned or scalded by the intense 

 rays of the sun. That injury occurred on some trees and not 

 on others near-by, and apparently growing under identical 

 conditions, is explained by the fact that the injured trees 

 probably were either further advanced or somewhat backward 

 in their development. However, as special observations were 

 not made during the period of injury there is no definite evi- 

 dence bearing upon this point. In all probability the injured 

 trees, except those most severely affected, will recover under 

 normal conditions next season, but the injury described has 

 caused a distinct check in their development. This trouble 

 should not be confused with a similar trouble described by 

 Dr. G. E. Stone in 1910^ and attributed to sun scald. The 

 latter was shown to be primarily due to root injury, either 

 through winterkilling or extreme drought, which prevented the 

 maintenance of a proper balance between absorption and trans- 

 piration, resulting in drying out and death of the needles. This 

 trouble occurred quite as frequently on the old needles as on 

 the young, while the trouble which appeared last season was 

 wholly confined to the newly formed needles. 



Several severe outbreaks of downy mildew on greenhouse 

 cucumbers were reported early in October. This belated 

 appearance of the disease was unexpected in view of its relative 

 unimportance during July and August, the period when nor- 

 mally it reaches its maximum development in Massachusetts. 

 The late occurrence of the disease may possibly be explained 

 by the wet weather of the latter half of September, and the 

 failure on the part of the growers to dry out their houses by 

 the use of heat and proper ventilation. 



The experiment to test the ability of the potato powdery 

 scab organism {Sj^ongospora snbterranea (Walbr.) Lag.) to pro- 

 duce the disease under Massachusetts conditions, noted in the 

 last annual report of the writer, was repeated the past season 

 with negative results. This evidence, added to similar results 

 obtained in other eastern States south of Maine, indicates that 

 powdery scab need no longer be considered as a possible menace 



1 Twenty-second annual report, Mass. Agr. Expt. Sta., 1910, pp. 65-69. 



