V] 



HYPOCREALES 



151 



As development proceeds the ovate or flask-shaped perithecia are dif- 

 ferentiated ; they always arise deep in the stroma and may remain completely 

 or partially immersed or may become superficial as they approach maturity. 

 Where they are more or less free the surface 

 of the head is usually rough, whereas when 

 they are entirely immersed it is smooth, 

 but in some cases the free perithecia stand 

 so close together as to produce a smooth 

 appearance. The cytological details of 

 development have not been studied ; the 

 perithecia arise from the vegetative cells 

 of the stroma and in no case have a;ny signs 

 of sexual organs been seen; it would thus 

 appear that Cordyceps is completely apoga- 

 mous. The first sign of the perithecium 

 is the differentiation of a knot of deeply 

 staining vegetative hyphae. 



The asci are long and slender with 

 slightly swollen apices into which the spores 

 do not penetrate; at maturity the contents 

 of the apex swell and the wall is ruptured. The spores are arranged in a 

 parallel manner, in a fascicle slightly twisted on its axis, and are nearly as long 

 as the ascus ; they are hyaline, very slender and almost always multicellular; 

 they break up readily into their constituent cells which, as already stated, 

 germinate separately to infect a new host. According to the investigations 

 of Lewton-Brain several nuclear divisions take place in the ascus before 

 spore-formation and the spores are multinucleate from their first inception. 



Two species, C. ophioglossoides (fig. nob) and C. capitata, are parasitic 

 on underground fungi of the genus Elaphoniyces and do not produce true 

 sclerotia ; for these reasons they are sometimes separated as another genus 

 Cordylia. 



Fig. III. Cordyceps Barnesii Thwaites ; 

 perithecia, x 170; after Massee. 



The species of Claviceps, like those of Cordyceps, possess filiform asco- 

 spores, and form sclerotia from which the stromata arise. The genus is, 

 however, much smaller, including only six species parasitic on various 

 Gramineae. Of these the best known is the almost cosmopolitan species 

 C. purpurea, the ergot, on rye and other cultivated grasses. 



The ascospores germinate on the flowers of the host, and give rise to 

 a mycelium which ramifies at first in the outer coats of the ovary and 

 ultimately fills its whole cavity, forming a sclerotium. Outside the ovary, 

 conidia are budded off, and at the same time a sweet fluid, the so-called 

 honey-dew, is excreted ; it attracts insects which carry the conidia with 



