THE FUNGI WHICH CAUSE PLANT DISEASE 579 



The more prominent forms as described are given below, recog- 

 nizing that some of them may be co-specific. 



B. cinerea Pers.''"-''' 



Hyphae slender, constricted at septa, gregarious, simple or 

 sparsely branched, erect, cinereous, conidia globose, pale. 



A form which occurs on the grape is usually referred to 

 S. fuckeliana though there is not entire agreement on this point. 

 On the grape the Botrytis develops its mycelium in the berries 

 and produces dense tufts of conidia over their surfaces. The 

 sclerotia form: within the fruits. Leaves and 

 canes are also affected, (see p. 140). 



On the lily Ward^'^ in a classic study de- 

 monstrated the parasitism of the fungus show- 

 ing its action to be dependent upon toxins and 

 enzymes. The t3T)e in this case deviated some- 

 what from the usual B. cinerea in that its 

 spores were a little larger than is usual, but it 

 nevertheless seemed to be this species. No 

 ascigerous stage was found. 



On Cyclamen and Primula Wehmer^'* re- 

 ports a similar case.-*" The fungus has also 

 often been reported on the cultivated gera- ^°- 388.— b. cinerea. 



^ ^ After Smith. 



mum. 



On lettuce Humphrey, "^ Jones, ^'* Bailey,''^* and many others 

 have reported a greyish mold on the leaves due to a Botrytis 

 which is often cited as B. cinerea though it appears to form no 

 ascigerous stage. The affected part of the leaf collapses and is 

 covered with a conspicuous growth of the conidiophores and coni- 

 dia. Small sclerotia are produced in considerable abundance 

 when on artificial media but they, on germination, bear clusters, 

 dense bushy tufts, of conidiophores. That this form on lettuce 

 ever produces ascophores is doubtful. 



Smith describes a case in which linden stems beginning at the 

 ground were parasitized by B. cinerea. The bark appeared to be 

 first affected and sclerotia formed in the cortical parenchjmia. 

 Similar cases are on record regarding the rose, various conifers, 

 grape (Brizi) Aesculus, Prunus. In all of these cases the Botrjrtis 

 seems to be B. cinerea and without ascophores. 



