Bean Anthracnose 117 



geneous and granular. Often there is a clear body resembling a vacuole 

 near the center, which Edgerton (1910:20) describes as a nucleus but 

 which earlier workers have regarded merely as a vacuole. Edgerton says 

 that as the spore ages it becomes vacuolate, and finally the contents 

 collect in small masses. The spores are no longer viable when this last 

 stage is reached. 



Spore germination 



In making germination tests, spores from young acervuli produced in 

 bean-pod cultures were transferred to a drop of the culture medium placed 

 on a flamed slide. The slides were transferred to sterile moist chambers 

 or petri dishes kept moist with wet blotting-paper, in which they rested 

 on glass supports to hold them up from the bottom. The temperature 

 was maintained at about 20° C. 



Germination usually takes place by the protrusion of a germ tube 

 from the side of the spore near one end and at an angle to its long axis. 

 On nutrient media some spores have germinated within eight or nine 

 hours (Plate III, 2). Bean agar gives the quickest and largest per- 

 centage of germination, although nutrient beef agar, potato agar, and 

 beef bouillon give nearly similar results. Soon after the protrusion of 

 the first tube, a second may be sent out from a similar point at the other 

 end. As many as four germ tubes have been observed coming from 

 a single spore, but rarely are there more than two. Dey (1919:307) 

 observed in a few cases more than two germ tubes developing from a spore. 

 The germ tubes form branches which radiate from it in all directions 

 (Plate III, 4). 



Germination takes place more slowly in water than in agar. A few 

 spores were observed to have germinated in water after eighteen hours 

 (Plate III, 10). In certain rain-water cultures about one-half of the 

 spores germinated in twenty-four hours, but this was a greater proportion 

 than the average. In distilled water, germination proceeded somewhat 

 more slowly. The majority of the spores in these water cultures became 

 uniseptate during germination, but septation was not observed to occur 

 so commonly in spores germinating in nutrient solutions. Often there 

 is a constriction of the spore at the septum. In some cases the spores 

 themselves increased somewhat in size before or during germination, 

 but this was not general and when spores were placed in nutrient solutions 



