Damping Off. 337 



tubes are quite sinuous, and at this age (seventeen hours from time 

 of sowing) were 15// to 25/./ long, and about 2/^ in diameter. In the 

 germinating spores are a few, 3 to 5, small and very strongly refrig- 

 erent granules in the hyaline and homogenous protoplasm, and are 

 quite well shown in the photomicrograph. On the following day 

 when the culture was forty hours old another photograph was taken 

 (iig. 47). By this time many of the conidia showed the development 

 of three tubes, and the tubes were now quite long. In some cases 

 the hyphae coming in contact, anastomose, one of these conditions 

 being shown in tlie photomicrograph. One day later several of 

 the conidia showed still other tubes, so that in time two to several 

 tubes may arise from a single conidium. The anastomosing in 

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

 of nntrient agar was quite thin and the conidia numerous, fruiting 

 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 dis- 

 tance 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 por- 

 tion act as a basidium also. In this cell culture there was not the 

 tendency for either the mycelium 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. 1, in the Petrie dish. 

 The conidia being so numerous in this dilution, caused the develop- 

 ment of numerous colonies in quite close proximity, and the fruiting 

 was necessarily more scanty and a less tendency to the develojDment 

 of the stroma so characteristic of the fungus on solid substrata, or 

 in the agar where they were not so crowded. There were, there- 

 fore, many scattering and independent fruiting hyphae or conidio- 

 phores. By placing a thin cover glass over portions of the plate 



22 



