
1891.] The Comparative Morphology of the Fungi. 1057 
process occurs in C. jonesii, in which is thus reached the full 
character of the conidium. 
Brefeld here adopts the familiar name previously applied to 
certain non-sexual spores, and extends to some extent, while in 
other directions limiting, its application, and gives it a definite 
morphological value. The conidium, then, may be defined as a 
reproductive organ, morphologically equivalent to the sporangium, 
and derived from it by reduction; or as a one-spored, closed 
sporangium. As the author well says, we have here a theoretically 
ideal series of stages, complete at every point. A similar set of 
steps leading from the sporangium to the conidium can be traced 
among the Oomycetous forms, although less aa and less 
convincing, 
Not only does the development of the andaba threads 
or conidiophores vary widely in different species, but within the 
limits of species it may be greatly modified by external condi- 
tions. The study of the structure and development of a very large 
series of forms of Basidiomycetes has shown that in some instances 
the true basidia characteristic of these fungi are accompanied or 
preceded by conidiophores which under certain conditions assume 
a form practically indistinguishable from the basidia; and the 
facts brought out lead irresistibly to the conclusion that the 
basidium, with its sterigmata and spores, must be regarded as a 
definite and unvarying conidiophore. Two species which show 
this relation very clearly are Pilacre petersii, which, formerly of 
doubtful relationship, is here shown to represent a special type 
of primitive Basidiomycete, and that which the author calls 
Heterobasidion annosum (= Polyporus annosus Fr. Trametes 
radiciperda Hartig). 
The basidia of the various Basidiomycetes are not of a single 
type, and cannot be referred to a common origin. Those of the 
simplest of the group are divided by cell-walls into several 
(usually four) parts, each of which gives rise to a sterigma and 
spore. And here we find two forms: basidia of elongated form, 
with transverse divisions, characteristic of Pilacre and Auricularia 
and of the Uredinez ; and basidia of rounded form, divided by 
walls parallel to their longer axes, occurring in the Tremellinee, 
Am. December.—2. 



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