46 THE LARCH CANKER 



show no such drops, or only a few very small ones, whereas 

 the dead segments are not noticeably more refractive than 

 the surrounding water, and contain numerous large drops. 

 These drops often escape fromthe dead cells into the surround- 

 ing water, and may then cling to the outside of the hyphal 

 walls. It was probably these drops which Willkomm (1867, 

 p. 206) described as ' micrococcussch warmer '. Occasionally 

 movement can be traced in them, but this is not a necessary 

 sign of life. The great variability in the size of the so-called 

 ' micrococcusschwarmer ' figured by Willkomm (Taf . xxiii, 

 24, E) is against their being bacterial cells (cf. Hartig's 

 criticism on p. 73). 



Willkomm states that the hyphae in culture may bear 

 lateral conidia, but though I have observed hyphae with 

 laterally borne bodies, like those figured in Taf. xxii, 24 c, 

 these bodies never became separated from the hyphae, and 

 they showed no inclination to germinate. 



Hyphae of a Penicillium bearing conidiophores and 

 conidia often turn up in drop cultures of the DasyscypJia. 

 This Penicillium grows on old apothecia of the DasyscypJia, 

 and it is often difficult to avoid collecting some of these 

 conidia when the ascospores are obtained. 



Pure cultures on nutrient media. The method of obtaining 

 -pure cultures of DasyscypJia calycina which I have found 

 most successful is this. Portions of bark with vigorous 

 apothecia of the fungus are placed on wet filter-paper in 

 the bottom of a drop-culture chamber, as described on 

 p. 42. A sterilized cover -slip is then placed over the top 

 and fixed with vaseline. Almost immediately the under- 

 side of the cover-slip becomes cloudy with condensed 

 vapour, and in the film of water so formed the spores ejected 

 from the apothecium remain attached to the cover-slip. If 

 the apothecia are giving off spores at the time when they 

 are put in the culture-chamber, these may be gathered in 

 an hour or two, but generally the chambers have to be 

 left till the next day, when sufficient spores will have 

 accumulated. 



Two culture-chamber rings are then placed on a slide 



