208 



Journal of Agricultural Research 



Vol. XV. No. 3 



fection of leaves of different ages occurs is a matter of conjecture, but it 

 is thought to be associated with the fact that younger tissues are more 

 susceptible. Probably the relatively small number of organisms which 

 retain their motility are able, when the stomata open, to establish them- 

 selves in the younger leaves, but are not able to gain a foothold in the 

 older tissues. 



The closure of the stomata may mechanically exclude the bacteria or 

 may interfere with stimuli which attract them into the interior of the 

 leaves. No attempt has been made to determine this point, but the first 

 theory seems to the writer the more plausible. 



FRUIT INFECTION 



Fruit infection occurs naturally without wounds. Stomatal infection 

 (fig. i) has been demonstrated in fruit artificially infected without 



wounding. Burger's (4) de- 

 scription of the effect on the 

 fruit is accurate in part, but 

 the softrot which he empha- 

 sizes results from organisms 

 other than the species causing 

 the small, circular, localized 

 spots on the fruit, characteristic 

 of angular-leaf spot infections. 

 The circular spots are at first 

 water-soaked in appearance. 

 Later their centers become 

 whitened, owing to a cracking 

 and drying out of the " tissues 

 (PI. 16, B). In fruit, as well 

 as leaf tissue, the bacteria 

 have been seen only in the intercellular spaces. 



Fig. I . — Cross section of epidermal portion of cucumber 

 fruit fixed eight days after inoculation with Bacterium 

 lachrymans, showing presence of bacteria in stoma and 

 tissues below. 



DISSEMINATION 



The means by which the disease is spread have been given a good deal 

 of attention because of the possible bearing which these might have on 

 remedial measures. Some of the observations and experiments may throw 

 light on other and similar bacterial diseases. 



BY RAIN AND WIND 



That the important relation of rainy weather to the progress of angular- 

 leafspot, a factor previously observed, was principally in the dissem- 

 ination of the causal organisms was made clear in the summer of 191 6. 

 Healthy potted plants which had been placed outside of the greenhouse 

 and at a distance of 4 feet from infected plants became diseased after a 



