246 



FUNGOUS DISEASES OF PLANTS 



Germination really consists in absorption of water, increase in 

 size of the sclerotial mass, and the pushing into growth, some- 

 times from many different points on the sclerotium, of compact 

 masses of hyphse, which develop into sporo- 

 phores. These sporophores may be from one 

 fourth to one inch in height, and they bear at 

 the summit head-shaped stromata within which 

 the perithecia are differentiated. A cross sec- 

 tion of the head-shaped stroma is shown in 

 Fig. 1 06, a. 



The sporophorc consists of a stalk from one 

 half to one inch in length, terminated by a 

 capitate enlargement about twice the diameter 

 of the stalk portion. In the stromatic tissue of 



FIG. 106. CLAVICEPS PURPUREA : SECTION OF STROMA AND ENLARGED 

 PERITHECIUM ; ALSO ASCI AND SPORES. (After Tulasne) 



the head numerous perithecia are formed near the periphery. So 

 far as is known, a perithecium is developed in two successive 

 stages : (i) By the repeated division of a few differentiated cells 

 below the surface there results an ellipsoidal pre-ascal tissue. (2) In 

 the proximal or basal portion of this cellular body an hymenium 



