126 Mortier F. Barrus 



and Wood were not working with a culture of the true bean-anthracnose 

 fungus but rather with one of the saprophytic forms which Edgerton 

 finds occurring commonly on old parts of bean and other plants. These 

 forms produce perithecia abundantly, but no conidia. In hundreds of 

 cultures of C. lindemuthianum examined by him, no perithecia have 

 been found, and he thinks that until more satisfactory proof is offered 

 of the presence of perithecia it is better to consider the bean anthracnose 

 fungus as lacking an ascogenous stage. 



Relation of fungus to host 



Penetration of the host 



Frank (1883b: 515) described in detail the germination of the spore and 

 the penetration of the host. He says that the spore, on germinating, 

 produces a germ tube, which on coming into contact with the epidermis 

 of the host forms an appressorium closely pressed against the surface 

 of the epidermis. This either remains unchanged, or after a time becomes 

 thinner and colorless on one side, and from this spot a germ tube appears. 

 The germ tube penetrates directly through the cuticle into the epidermal 

 cell, and either fills this cell with branching hyphae or quickly penetrates 

 the adjoining epidermal cells or those beneath. Voglino (1892), from 

 inoculations of parts of green bean pods, observed the germination of the 

 spore, the quick formation of large numbers of appressoria, and the produc- 

 tion of mycelial filament which penetrated into the interior of the epidermal 

 cells. Dey (1919) has carefully studied and figured this penetration from 

 stained sections made from material embedded in paraffin. He finds that 

 a peg-like infection hypha grows out from the surface of the appressorium 

 in contact with the host, which mechanically ruptures the cuticular layer 

 and then brings about a swelling and disintegration of the subcuticular 

 layers — probably by enzymic action. The infection hypha was never 

 observed earlier than forty-eight hours after inoculation. The rupture of 

 the cuticle is the result of the pressure exerted by the development of the 

 infection hypha. This hypha is very fine at first, but reaches a normal 

 size while growing in the cellulose layers below the cuticle. Here, or 

 farther on in the cell, it produces a small vesicle from which one or more 

 branches arise and extend into the host tissue. As the invading hypha 

 enters the cell, the protoplasmic contents collect around it, and later 

 a collapse of the cell takes place. The writer has never observed this 



