IO 



FUNGOUS DISEASES OF PLANTS 



FIG. 142. EFFECTS OF THE LEAF-SPOT 

 FUNGUS: PROLONGED CROWN 



nearly upright, although some- 

 what curled or rolled, present- 

 ing a characteristic appearance 

 in the field. 



Since the outer leaves are 

 the first to succumb, the plant 

 continues to develop new leaves 

 from the bud, and the crown 

 may thus become considerably 

 elongated (Fig. 142), at a seri- 

 ous sacrifice to root develop- 

 ment, and probably at great loss 

 to the sugar content. 



It has been stated by German 

 observers that the leaf-spot fun- 

 gus may also be found upon the 

 bracts, peduncles, and even upon 

 the seed pods. It is therefore 



thought that the fungus may be spread with the seed. 

 The fungus. When the leaf spots 



appear gray at the centers one may 



be sure of finding the conidiophores 



and conidia of the fungus in abun- 

 dance. The former arise in small 



clusters, apparently through the 



stomates at first. The base of the 



cluster is usually a few-celled stroma. 



The conidiophores are flavous, and 



ordinarily 35-55x4-5^. The co- 

 nidia are produced at the apices, and 



then by further growth of the conid- 

 iophores, slightly towards one side, 



noticeable geniculations are left, and 



the conidiophores are therefore flex- 



uous. The conidia are obclavate to 



needle-shaped, hyaline, many-celled, 



75-200 x 3-5-4-5 /* (Fig. 143). If 



produced under very moist conditions, 



FIG. 143. CERCOS/>OR.-I RKTICOLA: 

 CONIDIOPHORES AND CONIDIA 



