Bean Anthracnosb 147 



when the seed was in a more moist condition. Just how long the fungus 

 can live in old seeds has not been determined, although cultures were 

 obtained from seeds two years old. 



Infection studies 



Susceptibility of plants of different ages to infection 



But little evidence has been presented by investigators concerning the 

 susceptibility of plants of different ages to infection. Frank (1883 a: 34) 

 and others find that young and half-grown pods are more susceptible than 

 older ones. Edgerton (1908 : 397) remarks that the young bean plant is not 

 readily infected, but his later work (1910:41) indicates that he had but little 

 trouble in securing infection on seedlings. Cook and Taubenhaus (1912: 

 49), noting a correlation in this first statement of Edgerton's with results 

 which they had obtained on } r oung fruits of apple and pear with several 

 Gloeosporia attributed by them to the presence of an enzyme capable 

 of forming a tannin-like body toxic to fungi, tested the oxidizing power 

 of the enzyme present in the bean plant at various stages of its develop- 

 ment and found that the oxidizing power is greatest in the young bean 

 plant, is small during blossoming and the formation of young pods, is 

 large again when the plants have large green pods, and decreases again 

 when the pods are yellow. After making numerous inoculations on plants 

 at all stages of growth, the writer is convinced that a young bean plant 

 is more susceptible than an older one, and that young parts are more 

 susceptible than older parts. An experiment was made in 1910 in which 

 Refugee Wax beans were planted at intervals of seven and eight days 

 throughout the season, beginning on June 27 and ending on August 22. 

 In the evening of August 31, three days after the beans last planted ap- 

 peared, all plantings were inoculated by spraying a suspension of spores 

 over all parts of the plants. During the following day the plants were 

 protected as far as possible from drying out by placing wooden boxes 

 over the hills. When observed six days later, all the seedlings were badly 

 infected and some were dying. Good infection was obtained on the 

 younger leaves and petioles of beans planted one month earlier, but 

 slight infection on the older leaves. Those planted two months earlier 

 and having some mature pods were only slightly affected on leaves and 

 vines, but good infection was obtained on young pods. The nearly mature 

 pods showed no evidence of infection. The writer has always obtained 



