PENICILLITTM. 297 



starting to examine after four days. (2) Transfer some 

 gonidia to gelatine in sterilised Petri dishes. A good 

 medium is 5 per cent, gelatine made up with prune decoc- 

 tion and 40 per cent, cane sugar. In this medium cultures 

 can be kept for a long time, and will fruit readily a few 

 days after raising the temperature of the culture to 20 C. 



In suitable material showing the sexual organs note 

 (1) that thin branches arise from the mycelium; (2) 

 that the first of these hyphae to be formed in a group 

 is coiled like a corkscrew this is the archicarp or female 

 hypha ; (3) that other hyphae arise below the archicarp and 

 grow up to form a loose envelope around it one of these, 

 the antheridium, becomes applied by its tip to the apex 

 of the coiled archicarp, while the sterile hyphae form the 

 sheath of the fruit. 



In a mature ascocarp, treated with potash to make 

 it more transparent and mounted in glycerine, note (1) the 

 wall or sheath of the. fruit, consisting of a single layer of 

 cells, (2) the ovoid sacs or asci within, each ascus con- 

 taining eight ascospores. 



To see the asci and spores better, mount an ascocarp in 

 glycerine, crush it by pressing on the cover-glass, and note 

 (1) the ruptured ascocarp wall ; (2) the asci and the 

 spores, the latter being ovoid when young and having 

 when old a peculiar form notched at each end, like two 

 biconvex lenses fused together ; (3) the nutritive tissue 

 found only in young ascocarps, but absorbed when the 

 latter is mature. The ascospores contain about eight 

 nuclei ; they germinate like the gonidia. 



PENICILLIUM. 



430. Penicillium, found on all sorts of organic sub- 

 stances, from bread and jam to old boots and dried-up 

 ink, is the commonest of the Moulds. 



The mycelium is easily cultivated in a watch-glass of 

 Pasteur's solution to which gonidia are transferred from 

 an infected slice of bread. The mycelia soon appear as 

 floating white patches, which as they grow in area become 



