192 



FUNGOUS DISEASES OF PLANTS 



On blighted branches of the peach the mycelium has been 

 found (Smith) to grow most abundantly in the cambium and soft 

 bast, these tissues disappearing in large measure with the forma- 

 tion of extensive gum pockets (Fig. 71). 



The conidiophores arise as short hyphae, which soon become 

 septate at the extremities, branched and nodulose. The branching 

 proceeds in an indefinite and usually irregular or semidichotomous 

 fashion (Fig. 72, a and b). From the apex of these branches 

 toward the base conidia are rapidly cut off, these cells remaining 

 for a time simply moniliform or as branched chains, each con- 

 striction between the nodulations eventually marking the line of 



flg. 72. sclerotwia fructigena : conidiophores and conidia, 

 Section of Apothecium, Ascus, and Ascospores 



separation between adjacent spores. The spores germinate readily, 

 and often while still massed in the tuft of conidiophores, that is, 

 before being blown or brushed away. Germination studies, have 

 shown that many of the conidia may live through until the suc- 

 ceeding season, and, as indicated, the mycelium is even more 

 capable of effective hibernation. 



Ordinarily no apothecial stage has been observed to intervene 

 regularly in the life cycle of this fungus, and the ascosporous or 

 Sclerotinia stage is not believed to be important to continue the 

 propagation of the fungus. During the spring of 1902 the Scle- 

 rotinia stage was found (Norton) quite commonly in the orchards 

 of Maryland. The apothecia were discovered arising from scle- 

 rotia, which might be developed either within the tissues or on 



