(Edema of the Tomato. 



During the latter part of October, 1892, tomato plants, of a variety 

 No. 18, grown in the forcing houses of the Horticultural Department, 

 presented a very peculiar appearance. The plants were at some little 

 distance from the main passage way in the tomato house through 

 which I occasionally passed. For this reason, and also because no 

 complaint was entered by the growers, the trouble escaped my notice. 

 The plants presented to me the appearance of having been recently 

 transplanted, many of the compound leaves having a curved pendent 

 position, though the leaflets were usually curved strongly upward, 

 showing the lighter color of the under surface. It was suggested at 

 that time that this peculiar position of the leaf and curl of the leaflets 

 was a peculiarity of the variety. Upon each of the several following 

 visits to the forcing house, at intervals of four to six days, the peculiar 

 appearance of these plants fastened my attention for a few minutes. 

 Upon one visit I had occasion to pass the bench upon which they were 

 grooving, and I could not resist the impulse to look more closely at 

 the character of the curled leaf. 



It was at once apparent that this peculiar appearance was not nor- 

 mal to the plant. The veinlets as well as the midrib, petioles, and the 

 surface of the stem presented numerous elevated areas of a frosty 

 aspect as shown in figures 1 and 2, in Plate I, Their resemblance to 

 the masses of conidia formed in the early stages of some of the 

 Erysiphem was very striking. Examined with a pocket lens a mass 

 of minute rounded bodies could be seen which still boie resemblance 

 to conidia of the powdery mildews. The rounded particles possessed 

 a gleaming aspect and did not lie so loosely nor appear in chains as is 

 the case with these mildews. A little further observation showed that 

 great injury to the plant followed in the latter phases of the trouble. 



It was quite natural before recourse to a microscopic examination to 

 attribute the mildewed aspect of the leaves and the dying of the 

 leaves in the later stages to the operation of some fungus . But a 

 section through one of these areas revealed under the microscope a 

 very diJfferent state of things. The affected areas had the appearance 



