CULTIVATION 23 



on malt agar or on sterilized sawdust or blocks of wood. Etter 

 (1929), using a mixture of malt liquid, wood powder, corn meal 

 and starch in flasks, secured typical pileate sporophores of such 

 species as Lenwius lepideuSy Pleurotiis ostreatiis, Coprinus atra- 

 mentarhiSy C. Tnicaceiis, Polyporus pereniiis, P. farloivii, Gano- 

 derjna ciirtisii, and Trametes peckii. 



The incorporation of extracts from various fruits and vege- 

 tables into media may also stimulate fruiting by wood-rotting 

 fungi, but the sporophores on such substrata are sometimes ab- 

 normal. Long and Harsch (1918) used such media in studies 

 with wood-rotting species and concluded that the nature of the 

 substrate is of minor importance in stimulating the formation of 

 sporophores. They secured fruiting on plant-extract media by 

 the following species: Dae dale a juniper ina, Forties applanatus^ F. 

 pinicola, F. roseiis, F. robineae, F. texaniis, Irpex lacteiis, Len- 

 zites saepiaria, Pleurotiis ostreatus, Polyporus ajiceps, P. cinjia- 

 barinuSy P. dryophilus, P. farloiuii, P. obtusus, P. sulphur eus, Poly- 

 stictus hirsutuSy P. versicoloTy Trametes peckiiy and T. serialis. 



The studies by Badcock (1943) indicate, moreover, that the 

 nature of the substrate is a vital factor in the production of sporo- 

 phores in culture. He used sawdust as a basic material supple- 

 mented by readily available nutrients. As additional factors 

 there should be a plentiful supply of moisture in the substratum, 

 an atmosphere of high relative humidity, and exposure to dif- 

 fuse Hght of moderate intensity. Under these conditions Bad- 

 cock secured fructifications of 82 of the 92 species tested. 



The spores of many species, notably of the downy mildew^s, 

 powdery mildews, and rusts, can be germinated in w^ater, where 

 they will continue to grow until their reserve of stored food is 

 exhausted. Even though development is determinate under these 

 artificial conditions, observations of grow^th changes in water 

 contribute materially to the sum total of useful information. For 

 example, the oospores of downy mildews are notoriously refrac- 

 tory to germination, and hence an understanding of the necessary 

 environmental conditions, except for a few species, has not been 

 achieved. Hiura (1930), however, described a method for ger- 

 minating the oospores of Sclerospora graittmicola. A layer of 

 moistened cotton is placed in the top of a Petri dish and another 

 in the bottom, ample space being left between the layers. Moist 



