154 



MISSOURI BOTANICAL GARDEN. 



various vegetable and 



agar media, but no 



cultures ou 



mature conidia were developed. It therefore was not pos- 

 sible to inoculate with conidia from pure cultures. A few 



inoculations were made with the mycelium. Of these only 

 one or two were successful, indicating a low vitality of the 



fungus when under culture. 



The disease often has a striking appearance. The co- 

 nidia of the fungus apparently germinate on the surface of 

 the host and gain entrance through either the stomata or 

 wounds. The tissues are penetrated by the mycelium in 



* 



all directions, forming either a circular or elliptical spot, 

 which at first is darker in color than the adjacent tissues, 

 changing as the tissues die to either a brown or gray color. 

 The adjacent tissues of the host under moist conditions 

 turn brown and rot rapidly, the mycelium penetrating to all 

 parts of the leaf. Under less humid conditions, however, 

 the adjacent tissues slowly darken in color, often assuming 

 a purple tinge. It was found in such cases that there is a 



death of 



d 



the mycelium, indicating the presence of anenzyin secreted 



by the fungus. 



Bacteria are never associated with the 



latter type of the disease, but are often present with the 



former. 



The acervuli are usually formed in concentric rings. 



This character was so constant, that, taken along with 



other characters, it was thought at first that we have here 

 a new species of Colletotrichum. The examination of 

 both fresh and herbarium material at the Garden, at 

 "Washington, D. C, and elsewhere has 



elsewhere has revealed the fact 

 that such characters are variable and that the fungus is 

 probably identical with Colletotrichum Agaves Cav., de- 

 scribed as occurring on the cultivated agaves at Pavia. 

 The following is the description of our fungus : 



Spots circular or elliptical, often becoming confluent, olive, changing 

 to gray or brown; acervuli spherical to oblong, usually breaking through 

 the epidermis of the host in concentric rings and ejecting orange colored 



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