[Vorn 7 
82 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
upon its publication are Stereum hirsutum, S. striatum, S. 
purpureum, S. nitidum, and S. rugosum, no one of which was 
designated as the type species. 
The species of Stereum are here arranged in the usual sections 
of central-stemmed, lateral-stemmed, merismatoid, and dimid- 
iate and effuso-reflexed species; these sections are convenient 
for locating species approximately, but one should bear in mind 
that some species are ambiguous with regard to sectional charac- 
ters; all the species are probably so variable that individuals 
may be selected from most gatherings which will prove very 
misleading for study. For example, Stereum fasciatum is 
properly included in the section of effuso-reflexed species, yet 
fructifications of this species do occur now and then with elonga- 
tion of the umbo so great as to lead one to regard such a fructifi- 
cation as lateral-stemmed. 
While Stereum is a large genus in the number of its North 
American species, its difficulty is not proportional to the number 
of species, for the species of each of its several sections differ 
among themselves microscopically in the absence or presence 
of definite recognizable organs or combinations of organs, such 
as conducting organs containing latex (milk), vesicular organs, 
gloeocystidia, cystidia of various kinds, and noteworthy para- 
physes. In the determination of any species, one's effort is 
soon concentrated upon a small group of four or five species 
of common structure, some of which may be eliminated by 
geographie range, spore dimensions, etc. "The structural fea- 
tures have been very important in working out the extensive 
multiplication of species which had arisen in this genus through 
disregard of the work of earlier mycologists. 
As heretofore noted in the case of Hymenochaete, the east and 
west range of the species of Stereum is marked in comparison 
with north and south range; of our 77 species, only 7 range over 
both north temperate and tropical areas; the other 70 may be 
arranged in two groups, of which the 29 species comprising the 
northern group are in the region from Canada to the Gulf states; 
the other 41 species range from the Gulf states southward. The 
Gulf states are a region in which northern and southern species 
overlap in range. The excess of tropical and subtropical species 
over northern species is due to the small number of northern 
