3 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 35-55x4-5/4. 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 A* (^g. M3). H FIG. 143. CRRCOSPORA BETICOLA: 

 produced under very moist conditions, CONIDIOPHORES AND CONIDIA 



