Dec. 13. 191S Angular Leaf-Spot of Ciicumbers 469 



made. Some months later (September, 191 5) in a similar experiment 

 two out of four inoculated fruits became soft-rotted. These fruits were 

 from the market. All four showed the local gumming at the point of 

 inoculation (needle pricks) after five days, while check pricks gave no 

 gumming. Two days later two fruits began to soften, and the next day 

 the whole interior was swanning with bacteria. Plates were poured from 

 the interior of one of these fruits under sterile conditions, and again only 

 spreading fimbriate colonies were obtained. Smears from these colonies 

 stained by Van Ermengera's flagella stain gave rods with as many as 8 

 or 10 peritrichiate flagella. This organism grew well in the depths of 

 agar stabs and curdled milk with reddening of litmus in milk. The 

 other two inoculated fruits remained sound and after two weeks when cut 

 open showed only a very local infection not extending much beyond the 

 needle pricks in any direction. 



Since the organism causing the leaf-spot is polar flagellate and aerobic, 

 does not develop a fimbriate growth on agar,. and does not curdle milk 

 or redden litmus in milk, it is evident that this soft-rot was due to an 

 intruder, which may have come from the surface of the fruits, since they 

 were not sterilized, but only washed. 



When these fruits became soft-rotted, the suspicion arose that possibly 

 the softening and cracking of the stems and petioles (PI. XI/V, fig. 2) 

 might also have been due to some unsuspected soft-rot organism. The 

 inoculation experiments with Bad. lachrymans were therefore repeated 

 on stems and petioles of free-growing cucumbers with the same result as 

 before — i. e., softening and cracking of the younger stems and petioles. 

 From one of these stems platings were made and Bad. lachrymans 

 obtained in pure culture. At the same time several control inoculations 

 were made on stems and petioles, using a subculture of the fimbriate, 

 peritrichiate, soft-rot organism plated from one of the softened cucumbers 

 above mentioned, but no rot occurred (four weeks). This organism, how- 

 ever, soft-rotted green cucumber fruits when inoculated by needle pricks. 



Last of all, following the discovery of Traverso's paper, another set 

 of inoculations was made on cucumber fruits. Six marketable green 

 hothouse fruits were selected and inoculated with Bad. ladirymans. At 

 the end of 10 days in culture dishes at temperatures varying from 24*^ 

 to 30° C. all showed local gumming and infection about the needle 

 wounds, but none of them developed any soft-rot (PI. XlyVI, fig. 3). 



HISTOLOGY OF DISEASED LEAVES 



Pieces of a leaf that showed spotting were fixed on the second day, 

 embedded, sectioned, and stained. Stomatal infections were very 

 numerous (PI. XLVII, fig. i). The bacteria gorged the opening of the 

 stoma in some cases, as well as the cavity beneath it. Even a,t this 

 early date the bacteria had spread in great numbers for some distance 

 from the stoma, crowding apart or crushing the cells of the parenchyma 

 and causing a slight swelling on the leaf (PI. XLVII, fig. 2). 



