1907.] PUBLIC DOCUMENT — No. 33. 163 



less risk in planting in September, and scarcely any during 

 any time in October. If a house of cucumbers is planted in 

 August, it is necessary to ventilate freely, apply little or no 

 water to the foliage, and keep do\\Ti the moisture in the 

 atmosphere to the lowest degree, in order to hold mildews and 

 Anthracnose in check. 



Bacterial Disease of Lettuce. 



Our attention has been called at different times to an un- 

 describsd bacterial disease of lettuce, which is reported as 

 causing considerable damage in some localities. This disease 

 has been observed in our greenhouse for many years, and 

 during the year 1901 Mr. Percival C. Brooks, then a member 

 of the senior class in botany, investigated this problem. He 

 succeeded in isolating an organism from a diseased lettuce 

 plant, and obtained positive results from his inoculation ex- 

 periments with healthy plants. 



The disease in question has never been observed by us in 

 this State except in our o^\ti house, notwithstanding the fact 

 that we have for many years had occasion to carefully -study 

 the various lettuce crops in the State, and have constantly been 

 on the lookout for it. Neither has careful inquiry brought to 

 light any trace of a similar affection in lettuce houses in 

 Massachusetts. Since the disease occurred in our lettuce 

 house on crops which had been forced too rajDidly, it was 

 considered of little consequence and was given scarcely any 

 attention, inasmuch as we thought the trouble arose from 

 improper management of the crop. Our only purpose in call- 

 ing attention to this disease at the present time is that it is 

 reported as doing considerable damage elsewhere, particularly 

 in the south, which makes it desirable that we should be on 

 the lookout for it. The disease results in the appearance of 

 numerous small bro\vnish spots about the size of a pin-head 

 on the young and tender light-colored leaves of the head. The 

 spots are frequently quite numerous, and in some cases run 

 together, causing a destruction of a portion of the leaves of 

 the head. No attempt was made by Mr. Brooks to make any 

 extensive study of the organisms causing the disease, since at 

 that time it was bolieved to be of little consequence, and only 



