Family Solanaceae 325 



on the stems, usually attacking plants which are full 

 grown. It is also found as a saprophyte in the soil, 

 or growing on dead potato vines; or frequently 

 associated with silver scurf on the tuber. It was 

 previously thought to be a sclerotial stage of 

 Spondylocladium atrovirens Harz. Colletotrichum 

 atramentarium differs from most Colletotrichums in 

 that it produces an abundance of sclerotia both 

 on the host and in pure culture. It sporulates very 

 poorly but otherwise possesses all the characteristics 

 of the genus Colletotrichum. 



EARLY BLIGHT 

 Caused by Macrosporium solani E. and M. 



Early blight attacks the foliage only. Infection 

 seems to follow injury from insects such as the potato 

 beetle and the flea beetle. 



Symptoms. The disease is characterized by cir- 

 cular or irregular brown dry spots made up of a suc- 

 cession of rings (fig. 62 a). The spots may become so 

 numerous as to involve the entire foliage and cause 

 premature death of the tops. 



The Organism. The mycelium is brownish to olive 

 in color. The conidiophores arise through the sto- 

 mata of the leaf. The conidia are produced singly, 

 the body of the spore has from 4 to 12 transverse 

 septa, with few longitudinal cross walls (fig. 62 b). 

 When germinating, a germ tube may be produced 

 from each cell of the conidia. This penetrates the 



