47 
THE EVOLUTION OF THE BASIDIOMYCETES.* 
G. MASSEE, F.L.S., 
At'ii 1 . 
There are three primary groups of fungi, as recognized from 
a morphological standpoint, (i) Phycomycetes, characterized 
more especially by the presence of sexual reproductive bodies, 
and mostly of functional value. The members of this group 
are mostly aquatic in habitat, and are by many considered 
as being derived from the algae, which in many instances they 
closely resemble, but differ in the absence of chlorophyll, 
hence they are dependent on organic food material. All the 
species are minute, and are not so well known to mycologists 
generally as they should be, considering their abundance in 
this country. This is perhaps because they are more inter- 
esting from a cytological than from a systematic standpoint, 
and do not loom up conspicuously at a fungus foray. (2) 
Ascomycetes. In this group, as in the following, sexuality 
has completely disappeared, hence the anxiety respecting 
possible hybrids, which is ever before the student of the 
higher plants, is unknown to the mycologist dealing with 
these groups. However, extreme variability within a given 
genus, or even a given species, is often present, and is a source 
of equal uncertainty. The leading character in distinguishing 
the Ascomycetes is purely morphological, and perhaps arbi- 
trary. It depends on the spores, the equivalents of seeds in 
the higher plants, being produced within special cells. This 
one structural feature is common to many thousands of 
species of fungi, of very various shapes and sizes. (3) Basidio- 
mycetes, as opposed to the Ascomycetes, are characterized bv 
the spores being borne outside special cells, usually at the tip. 
Here again thousands of species are linked together by this 
one structural feature, which is possessed by the larger, and 
generally best known, as the toadstools, mushrooms, puffballs, 
etc. As previously stated, the primitive fungi included in 
the Phycomycetes were either decidedly aquatic, or inhabitants 
of damp localities, and the spores of all such possessed the 
power of spontaneous movement in water, due to the presence 
of slender cilia, and are known as zoospores. By means of 
the motile power possessed by the zoospores, the distribution 
of the fungus was effected. However, by such means the 
Phycomycetes were restricted to an aquatic habitat, or to 
those places where a film of water was present, in which the 
zoospores could travel. In the Phycomycetes we perhaps see 
the starting-point in the evolution of a group of organisms. 
* Given at the meeting of the Yorkshire Mvcological Committee at 
Sandsend.) 
191 1 Feb. 1. 
