1898.] PUBLIC DOCUMENT — No. 33. 55 



these decayed stems and roots no one organism could be 

 found as the cause of the rotting. Bacteria (mostly micro- 

 coccus) swarmed in all aftected parts, and several mould 

 fungi also occurred. Quite noticeable on all affected plants 

 was the occurrence on tubers and even on the base of the 

 stem, of small, white, mealy dots, scattered abundantly 

 over the surface. These were apparently enlarged lenticels, 

 being composed of parenchymal cells breaking out at the 

 surface. It seems probable, or is at least possible, that their 

 production was due to the scarcity of air in the wet soil. 



We can only conclude here, as in the other case, that this 

 cannot be called a definite disease, but rather was the result 

 of abnormal and unusual conditions. During the long-con- 

 tinued rain the living functions of the plant were disturbed 

 and its ijrowth checked. Various oro:anisms then came in, 

 and, gaining a foothold, so weakened it that when the sun 

 came out it wilted down and in the worst cases died. Had 

 it been possible to thoroughly cultivate and stir the soil 

 at this time, it is reasonable to suppose that much of the 

 trouble might have been averted ; but the extreme wetness 

 made such a course impossible. 



This trouble came on after the potatoes had reached a 

 marketable size. We therefore recommended digging them 

 in all affected places, in order to save them from decay. Be- 

 yond this there could be no practical treatment suggested. 



Early in August, or even sooner, the real potato blight 

 or rot, Phytophthora infestans, began to appear, and devel- 

 oped very extensively during the month, killing the tops of 

 potatoes everywhere, and causing great loss by rotting of 

 the tubers. This disease is too well known to need ex- 

 tended description. Its ravages might probably have been 

 controlled to some extent by thorough spraying throughout 

 the season, but it would have been practically impossible to 

 entirely prevent it in such a summer. 



The "Drop" of Lettuce. 

 The loss represented by this disease frequently amounts 

 to thousands of dollars in a single season in Massachusetts. 

 Almost every lettuce grower has had more or less experi- 



