the Genus Cordyceps . 3 
external or cortical hyphae being usually tinged with colour, 
and in many species giving off numerous short lateral 
branches, which form the minutely velvety or downy exterior 
of the stem. The fertile portion, described in systematic 
works as the ' head 5 or ‘ club,’ is usually terminal on the stem- 
like sterile stroma, and varies in form in different species 
from globose to clavate or cylindrical ; in some few species 
the fertile portion is situated below the apex of the stem, 
or several fertile branches spring laterally from the upper 
portion of the stem. In structure the ascigerous portion, 
like the stem, may be composed of more or less parallel 
septate hyphae ; not unfrequently the hyphae coalesce laterally 
and the compound cells are of various lengths, but much 
of the hyphal origin is still evident; in a few species the 
coalescence of the hyphae is complete on all sides, and the 
septa more numerous, so that the component cells present 
a polygonal outline irrespective of the direction in which the 
section is taken, and consequently resemble a true parenchy- 
matous tissue. 
The perithecia always originate deep in the stroma, and 
stand side by side, their mouths reaching the surface of the 
stroma. In form the perithecia are ovate or flask-shaped, 
and may remain completely immersed, or at maturity be 
quite superficial, the whole of the perithecium being exposed, 
and attached to the stroma by the extreme base ; transitional 
stages connect the two extremes. As a rule, when the 
perithecia are more or less free from the stroma, the surface 
of the head is rough, whereas when they are completely 
immersed, it is smooth ; but a section is always necessary 
in cases where the surface of the head is smooth, as in some 
species where the perithecia are entirely superficial, only very 
slightly narrowed at the mouth, and closely crowded, they 
form an almost even surface, as if immersed. 
The asci always contain eight spores, are very long and 
slender, have a slight swelling at the apex, and are hence 
described as capitate. The function of the capitate apex 
is to effect dehiscence when the spores are mature ; at this 
