254 Report of the Department of Botany of the 



(b) Another striking symptom, but visible only in June and early 

 July, is the peculiar yellow coloration of the foliage and the dwarfing, 

 crimping, and curling of the leaves. Fig. 4 (Plate V). As-the season 

 advances the yellow color usually disappears, but the small crimped 

 leaves still persist. The grower is sometimes deluded into believing 

 that his vines have grown out of the disease. Careful examination 

 the next year, however, will show that the vine is either dead or in 



a much more 

 weakened con- 

 dition. 



(c) Vines are apt 

 to die at any time 

 of the year although 

 most of them seem 

 to die in the winter. 

 Presumably their 

 feeble growth of 

 the preceding 

 summer makes 

 them very suscep- 

 tible to injury by 

 frost and cold. 

 Fig. 6. It is not 

 unusual, however, 

 to find a vine wilt- 

 ing in midsummer. 



(d) I n certain 

 instances one may 

 find peculiar longi- 



The excrescence is 



Fig. 



6. — Longitudinal Section of Trunk and Arm of 

 Vine Shown in Plate II. 



(Position of arms reversed.) 



tudinal ribbed excrescences on the trunk or arm. 

 not tuberculate as in the case of crown gall, and it does not possess 

 the fleshy consistency of a crown gall tumor. Nor does the 

 excrescence have the appearance or consistency of the hard 

 tuberculous outgrowth which follows winter injury. 2 



2 Particular mention is made of these facts because they correct certain mistakes 

 of the former bulletin. The vine shown in Cornell Bulletin 263, fig. 45, is attacked 

 by crown gall as well as dead arm, and the lesions shown in this figure and in 

 figure 46 are caused by the crown gall organism, B. tumefaciens. The lesion 

 shown in figure 47 is probably of similar origin, as it came from a vineyard 

 in which practically all the vines are infected. When in the vineyard on July 

 21, 1909, very evident lesions of the dead-arm disease were found on two shoots. 



