ASCOMYCETES 



237 



In the same way as for the cotton, so also in the case of the 

 cowpea, resistant races have been found. The most resistant of 

 the original varieties tested was the form known as Iron Moun- 

 tain, which has since been considerably crossed, and in various 

 ways improved. 



The fungus. It has been stated that this fungus is unques- 

 tionably very generally distributed and may live indefinitely in 

 the soil. This is due to the fact that it is easily propagated 

 in a saprophytic manner and may therefore live in all probability 

 a long period of time without the intervention of the parasitic 

 habit. The fungus gains entrance to the host through the soil, 



FIG. 99. NEOCOSMOSPORA VASINFECTA. (c after Erw. F. Smith) 

 a, the fungus in xylem of stem ; b and c, conidial stages from cultures 



and hence through the root system. This is believed to be the 

 sole method of infection with the form on cotton and cowpea. 

 It is also believed that healthy plants are directly affected with- 

 out the assistance of any other organism or mechanical effect 

 causing an injury through which the fungus might obtain access. 

 The mycelium of the plant is at first found most abundantly in 

 the vessels of the xylem (Fig. 99, a) ; but in later stages of the 

 disease it may pervade other tissues. Upon the death of the 

 plant it comes to the surface along the lines of least resistance ; 

 hence it appears lineally distributed in the areas between the 

 vertical - lines of bast. The fungous hyphae are, as they occur 

 in the host plant, yellowish in color, considerably septate, and 

 irregularly branched. According to Atkinson conidia may be 



