1918.] PUBLIC DOCUMENT — No. 31. 33 a 



DEPARTMENT OF BOTANY. 



A. VINCENT OSMUN. 



The activities of the department of botany during the last 

 year have continued mainly along two lines, viz., plant pathol- 

 ogy and plant physiology. In addition, seed work, corre- 

 spondence and reorganization of the mycological collection have 

 demanded increased attention on the part of the staff. 



A survey of the season of 1917 in Massachusetts indicates 

 that, on the whole, conditions were somewhat unfavorable for 

 the development of parasitic fungi. A late, wet spring, followed 

 by a period of drought, checked many diseases which early in 

 the season had threatened serious loss. Occasional short periods 

 of high humidity were usually accompanied by high tempera- 

 tures, which prevented development of potato late blight, and 

 were followed by unusually bright weather not favorable to 

 uninterrupted development of other diseases. 



Early blight of potato inflicted more than the usual amount 

 of damage before being checked by the dry weather of July. 

 The tendency on the part of potato growers to delay the first 

 application of Bordeaux mixture was responsible for much of 

 the injury from this source. The first application, when the 

 plants are not over 6 to 8 inches high, is one of the most im- 

 portant in the spraying schedule, as it is at this stage more than 

 any other that a coating of the fungicide on the foliage is 

 needed to prevent the early and late blight fungi from obtain- 

 ing a start in the tissues. Late blight of potato was severe in 

 the island counties and along the coast, owing to the continued 

 high humidity throughout the season, the normal condition in 

 that part of the State. The disease was present at scattered 

 points in other parts of the State, but in few instances was in- 

 jury to the vines sufficient to cause alarm. Later, however, 



