A. Sharples 165 



out. Cultures were successfully established from conidia by carefully 

 rubbing away the upper layers of old spores with a sterile needle, using 

 young spores from beneath to inoculate test-tubes of potato-mush agar. 

 These cultures when transferred to flasks showed an interesting transition, 

 indicating that the zoning of the cultures is variable, depending largely 

 on external conditions. PI. VI, figs. 15-17 show a series of photographs 

 of flask cultures originating from the conidia. Figs. 15 a and 15 b show 

 a cidture zoned on both surfaces. Fig. 16 a shows the zoning on the upper 

 surface, but the photograph of the under surface 16 b shows that the 

 zoning does not extend through the substance of the culture as in a 

 typically zoned one. Fig. 17 b shows the under surface of a non-zoned 

 culture, exactly similar to the under-surface shown in Fig. 16 b while 

 Fig. 17 a shows the typical under-surface of a zoned culture. 



The action of the light on the zoning was tested by inoculating flask 

 cultures with small pieces of the crust taken from a zoned one. These 

 cultures were allowed to grow for a few days till the zoning became 

 ajDparent in all of them. At this stage some of those showing two or 

 three rings were placed in the dark, the other allowed to stand in diffuse 

 light in the Laboratory. The latter developed into zoned cultures. In 

 those placed in the dark the zoning stops immediately. The zoning of 

 the fungus in pure culture is not constant, but can be varied by chang- 

 ing the conditions under which it is growing. 



Fructifications were not obtained in pure culture till the end of 

 1916. It was then found that if sufficient water is placed in the culture 

 tube to cover the cotton wool and partially immerse the wood block, the 

 fungus immediately commences to produce growths resembling fructifi- 

 cations. The top end of the wood block must project slightly above the 

 surface of the water and be kept comparatively dry in order to provide a 

 suitable place for inoculation. The fungus quickly strikes away, and 

 growing down the block through the water produces thin, black plate- 

 like structures resembling the plate-like fructification found in nature. 

 The fungus grows through the cotton wool and in one case produced the 

 "Kretschmaria" form on the lower end of the wood block. Two or three 

 weeks after the "Kretschmaria" form was noticed, small protuberances 

 appeared on the upper end block which finally took on the "Xylarial" 

 form; these were black stalked with a small greenish-grey head. The 

 latter colour was due to the production of the typical conidial layer. 

 Slants were started from these conidia, and typical cultures obtained. 

 Thus the whole cycle of the life history has been obtained with the 

 exception of the ascospore stage. 



