ORIGIN OF THE BASIDIOMYCETES. 443 
Isaria, Pers., a genus included in the Hyphomycetes, and 
containing about eighty species, is closely allied to Stilbum and 
Tubercularia, differing more especially in the component fascicle 
of hyphe not being cemented into a compact mass, but remaining 
loose and open, consequently the fertile head is spreading and not 
globose (PI. 16.fig. 18). About twenty-two of the so-called species 
of Isaria are known to form the conidial condition of species of 
the ascigerous genus Cordyceps, Fries, which for the most part 
are parasites on the bodies of various insects. The remaining 
species grow on wood and various decaying vegetable matter, 
dung, &c., and in all probability do not at the present day include 
any ascigerous phase in their cycle of development. 
Isaria pulcherrima, Berk. & Broome, a beautiful species 
forming delicate feathery, erect tufts on hard wood, has basidia 
not at all distinguishable from those of Stlbum vulgare (Pl. 16. 
fig. 19); and an examination of numerous species of Isaria shows 
exactly the same sequence of structure of the basidia as that 
already described under Stilbum and Tubercularia. 
Many striking examples of characteristic Protobasidiomycetes, 
allied to one or other of the three genera mentioned above, 
are described and beautifully figured by Möller in his excellent 
work on Brazilian Protobasidiomycetes (10); among others may 
be mentioned Pilacrella delectans, Moller, which resembles in 
general aspect and morphological details Isaria pulcherrima, 
Berk. & Broome. 
It has already been stated that, even from the standpoint of 
the systematist, basing his conclusions on features presented by 
mature structures only, there is no valid difference between the 
genera Stilbum and Tubercularia: many members of both genera 
are known to represent the conidial condition of species of Nectria, 
whereas other members are almost certainly self-sustaining in 
every respect, having no other form of fruit included in their 
life-cycle. 
Tsaria, again, is very closely allied to the two preceding genera, 
differing only in the less compact sporophore ; many species are 
proved conidial stages of ascigerous forms, as Cordyceps; others, 
again, possess no higher phase of reproduction. 
Finally, in all three genera we find exactly the same sequence 
of progression in the form and structure of the basidia, from 
what may be termed the conidiophore type, having elongated, 
unthickened spore-producing hyphal cells, to very short and 
