148 Moetier F. Barrus 



good infection on pods of susceptible varieties when inoculated under 

 favorable conditions for infection before they passed their brittle, or 

 "snap," condition. 



Susceptibility of different parts of the plant to infection 



As mentioned in the preceding paragraph, Frank (1883 a) says that young 

 bean pods are more subject to attack than are older pods, and this has been 

 noted also by other early writers. Frank further found the pods to be more 

 susceptible than the stems, the leaves, and the petioles, although inocu- 

 lation on young bush beans resulted in the appearance of lesions on the 

 hypocotyl, the epicotyl, and the veins of young leaves. He found the 

 cotyledons especially susceptible. Scribner (1888) states that parts of 

 the plant other than the pods and the seeds are rarely attacked. Edgerton 

 (1910:42) found that when bean seeds were inoculated with spores of the 

 fig- and the cotton-anthracnose fungi, these organisms were able to attack 

 and grow in the semi-living cotyledons but did not infect other parts of 

 the plants. However, the cotyledons are to be regarded rather as culture 

 media than as host tissue. Lauritzen (1919:33) says the secondary leaves 

 of the bean are more pubescent and seem to be affected more easily at 

 the limiting humidities. This seems to be due to favorable humidity 

 rather than to susceptibility. Others, in writing on the subject, have 

 usually described the disease as occurring on the leaves, the stems, the 

 pods, the seeds, and the cotyledons. The writer has found all young parts 

 of the plant, including the roots, subject to attack, but as they become 

 older they grow more resistant. The tissues of the seedling and of the 

 young pod appear to be the most susceptible. The epicotyl of young 

 bean plants of varieties showing marked resistance to the disease has often 

 become affected when the plant was inoculated, although the other parts 

 showed no lesions. In such cases, resistance may be due to the inability 

 of the infection tube to penetrate the cuticle. 



Susceptibility of different varieties of Phaseolus vulgaris L. to infection 



In a number of the treatises on bean anthracnose, certain varieties are 

 mentioned as being more susceptible to the disease than other varieties, 

 but in most cases no inoculation experiments have been conducted to 

 confirm these statements. Frank (1883 b: 511) says that Lindemuth 

 observed the disease on the red-mottled Zucker-Stangenbohnen while other 



