V] HYPOCREALES i49 



authors found some evidence that a first nuclear fusion takes place in the 

 ascogenous hypha before the differentiation of the asci. 



The ascus is formed in the usual way from the penultimate cell of the 

 hypha; the usual nuclear fusion and successive nuclear divisions take place 

 during its development. 



In the genus Podocrea, the strorha is erect, and sometimes branched; in 

 Hypocrea it is usually hemispherical or bolster-shaped and is colourless, or 

 yellow or brown in colour. The majority of species occur saprophytically 

 on wood, or as parasites on the larger fungi. In both genera and in 

 their immediate allies, the spores are two or more celled. The systematic 

 position of Podocrea alutacea^ has undergone curious vicissitudes; in con- 

 sideration of its form it was at first placed among the Basidiomycetes as 

 Clavaria simplex, later it was regarded as a compound structure, the pyreno- 

 mycetous fungus being held to be parasitic, according to different authors, 

 on Clavaria ligula and on species of Spathularia. The stalk being thus 

 attributed to another fungus, the ovoid perithecial portion was referred to 

 the genus Hypocrea. The question was set at rest by Atkinson, who succeeded 

 in growing the normal upright stromata in pure culture from ascospores 

 alone, and thus demonstrated that only one fungus was concerned. 



The species of Epichloe occurparasitically on grasses the stems of which 

 become coated by the stromata. The stroma is at first white, then yellow; in 

 the early stages of its development oval conidia are produced, later the peri- 

 thecia, which are completely embedded in the stroma, reach maturity; the 

 ascospores, like those of the remaining genera of the Hypocreaceae, are fili- 

 form; Dangeard has shown that they are at first elliptical and uninucleate; 

 later they elongate, the nucleus divides and the spore undergoes septation. 



The genus Cordyceps (fig. i lo) includes about sixty species ; these are 

 mainly tropical forms parasitic on insects, the bodies of which they transform 

 into sclerotia from which the stromata grow out. The peculiar appearance 

 of these structures has given rise to curious views as to their significance 

 and medicinal va,lue; thus Berkeley reports that Cordyceps sinensis is a 

 "celebrated drug in the Chinese pharmacopoeia, but from its rarity only used 

 by the Emperor's physician." The striking belief that it is "a herb in 

 summer and a worm in winter," may perhaps sufficiently account for the 

 esteem in which it was held. 



The ascospores are multicellular and filiform and when shed break up 

 into their separate cells. Germ-tubes from these, or from the conidia, infect 

 the insect either as a caterpillar or chrysalis, and penetrating into its interior 

 give rise to cylindrical conidia which enter the blood-stream and increase 

 by yeast-like budding till the insect dies. A mycelium then appears and 



1 Podocrea alutacea lAnAaxL^ Podosiroma alutaceum (Pers.) Atkinson. 



