[Vor. 5 
302 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
have been confused by some authors with setae and have led 
to the publication of several such species under Hymenochaete. 
Istvanffit has shown that there is a fundamental difference 
between such organs and the conical, pointed setae which are 
charaeteristie of Hymenochaete. In any doubtful ease which 
the student may meet it would be well to aid conclusion by the 
color reaction with solution of potassium hydrate already 
mentioned. In my experience the dimensions of setae are not 
suffieiently constant to hardly more than grade these organs 
as large, medium, and small. 
According to our present knowledge, Hymenochaete attains 
its greatest development both in form and in number of 
species in the western continent where it culminates in a small 
group of indigenous stipitate species. Temperature condi- 
tions are important in the geographieal distribution of the 
species of this genus; this is shown by the long east and west 
range across North America of common species, in compari- 
son with the much shorter north and south range. Further- 
more, Hymenochaete is a genus of tropical species rather than 
of the cooler portion of the north temperate zone, for in con- 
trast with the 29 species occurring from the Gulf States to 
Brazil only 13 species are known north of the latitude of Vir- 
ginia, and from Europe perhaps 9 species, of which 6 are well 
known. 
Original descriptions of the species of Hymenochaete have 
required considerable modifieation with regard to characters 
referring to form, because they were based upon too limited 
an amount of material. In the ease of species of T'helepho- 
raceae growing on prostrate logs, the inclination of the sub- 
stratum at the point of attachment and the position of the 
substratum as to whether over or under the fructification are 
important in determining the habit and form of the fructifica- 
tion. For example, a species present in quantity on a log 
slightly raised above the ground will often show fine resu- 
pinate specimens on the under side of the log; about an eighth 
of a ci ference up the side of the log the upper margin 
is reflexed, becoming longer reflexed and with a shorter resu- 
1 Physiologische Anatomie der Pilze. Jahrb. f. wiss. Bot. 29 : 410. 1896. 
