[Vor. 5 
178 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
iomycete, and finally referred by Fries with doubt to Cor- 
ficium and regarded by Quelet as a Cyphella. 
Into Aleurodiscus have been assembled species of related 
structure which were originally published in Corticium and 
Stereum on the basis of form of fructification, but which are 
noteworthy by basidia and spores often enormous in dimen- 
sions for the genera to which these species were originally 
referred, and which sometimes have paraphyses of remark- 
able form, and the fructification greatly thickened in some 
species by so large an amount of incrusted or granular mat- 
ter as to render it very difficult to make out the detailed struc- 
ture of basidia and paraphyses in good sectional prepara- 
tions. The granular and crystalline matter may be dissolved 
from the sections by warming them on the slide in a few drops 
of dilute hydrochloric acid, but with the disadvantage of leav- 
ing the paraphyses and other organs with rather vague out- 
lines, as though somewhat collapsed or disorganized. 
Some species now referred to Aleurodiscus are intermediate 
between this genus and other genera by the absence of any 
notable development of some one or other of the foregoing 
charaeters, and it is too largely a matter of personal opinion 
as to just which species should be transferred. On the whole, 
Aleurodiscus is probably useful, although bound to be a source 
of eonfusion by introducing into a scheme of classification 
based upon form and general structure of fructification a con- 
flicting scheme of classification based upon rather trivial, and 
often poorly shown, features of microscopic detail, with dis- 
regard of diversity in form and general structure of fructi- 
fication involved. Innovations of this kind should certainly 
be exceptional. 
Of the 25 species of Aleurodiscus which have been recog- 
nized up to the present time, 14 occur in North Ameriea, 8 
in Europe, 5 in Asia and Australia, 2 in Africa, and 2 in 
South America. A. acerimus is the only one of these which 
is of world-wide distribution; 4. amorphus is the only other 
species common to both Europe and North Ameriea, and in 
North America it is restricted to northern United States 
and Canada. Only 3 species, A. acerinus, A. candidus, 
