DAMPING OFF. 263 



some cases is quite common. In this cell culture where the layer 

 of nutrient agar was quite thin and the conidia numerous, fruit- 

 ing did not take place very abundantly. In many cases the 

 basidia are directly connected with the conidium, and in other 

 and a majority of cases the basidia are developed from the hyphae 

 at a variable distance from the conidium. The basidia under 

 these circumstances are usually simple, terete and at the apex 

 bear several conidia, which because of the rather large per cent, 

 of water in the medium soon free themselves from the point of 

 their origin and rest at one side. In a few cases the basidium is 

 branched, or the fruiting hypha may bear lateral or opposite 

 branches, and the terminal portion act as a basidium also. In 

 this cell culture there was not the tendency for either the mycel- 

 ium or the basidia to become swollen or enlarged. Two photo- 

 micrographs were taken of the conidium production in the cell 

 culture, one showing the development of a basidium directly from 

 the conidium (50 lower left) and one with two basidia near each 

 other on a single thread of the mycelium (48 middle right). 



In order to study the separate conidiophores, or fruiting hyphae 

 recourse was had to the dilution culture, No. i, in the Petrie dish. 

 The conidia being so numerous in this dilution caused the devel- 

 opment of numerous colonies in quite close proximity, and the 

 fruiting was necessarily more scanty and a less tendency to the 

 development of the stroma so characteristic of the fungus on solid 

 substrata, or in the agar where they were not so crowded. There 

 were therefore many scattered and independent fruiting hyphae or 

 conidiophores. By placing a thin cover glass over portions of the 

 plate these erect conidiophores were bent in a prostrate position, 

 and the amount of moisture was sufficient to displace the greater 

 amount of air so that the medium between the glass and the agar 

 was nearly of the same density as the agar itself, and quite satis- 

 factory photographs could be obtained when the subadjacent 

 growth of mycelium was not too dense to interfere with the entrance 

 of light, or to produce a hopeless confusion of threads which were 

 not desired. Figs. 49, 51 and 54 represent some of the conditions 

 of the conidiophores in this culture, which have been referred to 

 above. (Figs. 46-51 and 54 were photographed at an amplifica- 

 tion of about 600 diameters). 



A portion of one of the fruiting stools which was teased out 



