5 
the Genus Cordyceps \ 
The fact that Isaria farinosa can develop its characteristic 
fructification as a saprophyte on other than on insect sub- 
stratum, demolishes the argument that those so-called species 
of Isaria not occurring on insects cannot be the conidial of 
species of Cordyceps. 
Numerous species of Cordyceps have no correlated conidial 
form, and on the other hand, still more numerous forms of 
Isaria exist, which at present are not suspected of being 
connected with any known species of Cordyceps. Among 
the latter may be mentioned more especially Isaria densa , 
Fries, which has been brought into such prominence by the 
admirable researches of Giard 1 . This fungus is parasitic on 
the larva of the cockchafer, known in different parts of France 
as vers blancs , turcs , mans , &c., and is well known as one 
of the most serious of insect scourges with which French 
agriculturists have to deal. Giard has clearly demonstrated, 
after years of patient research in the laboratory and in the 
field, that the conidia of Isaria densa can be utilized under 
certain conditions as an inoculation-medium, resulting in the 
wholesale destruction of the larvae. 
The form-species of Isaria which can with the greatest 
amount of probability be considered as conidial conditions 
of species of Cordyceps , assume different forms of develop- 
ment, as shown by Atkinson and Giard, frequently appearing 
first as an effused, more or less velvety or cottony layer — 
the Botrytis- form, — and afterwards, influenced by unknown 
conditions, passing on to the more complex, erect or stipitate 
form known as Isaria ; during this phase of development the 
sclerotium is formed within the body of the host, and finally 
the ascigerous form appears. Numerous species belonging 
to the form-genus Isaria are only known at present as sapro- 
phytes, growing on dead and usually more or less decomposed 
wood, bark, leaves, flowers, &c. ; others are met with on 
decaying fungi or on dung ; on the other hand, some species, 
1 Z’ Isaria densa (Link) Fries, Champignon parasite du Hanneton commun 
(■ Melolontha vulgaris L.) ; Bull. Scient. de la France et de la Belg., Tom. XXIV, 
pp. i —i 1 2, 4 pi. (1893). 
