Oct. 1902] 
North American Ustilagineae 
131 
also been changed from Ustilago to Cintractia. Sphacelotheca 
and Cintractia are not considered good genera by some botanists 
though apparently they deserve such recognition. As considered 
here Sphacelotheca is characterized by the possession of a false 
membrane of definite sterile fungous cells, that envelopes the 
sorus before its rupture. Groups of these sterile cells are also 
often found within the spore-mass. There is also present 
a central columella, usually composed of the remains of the plant 
tissues, and the spore mass when young shows a centripetal devel¬ 
opment around this. Because of this method of spore develop¬ 
ment certain of these species, as well as a few Ustilagos, have 
been placed under Cintractia by some botanists. Cintractia 
(including Anthracoidea of Brefeld), however, is characterized 
by spores, usually of a peculiar black-brown color, that develope 
gradually in a centripetal manner forming a sorus that remains 
rather permanently and firmly agglutinated. Species of this 
genus also often have more or less evidence of a false membrane 
and a columella. They occur usually on the Cyperaceae or on 
related families. The genus Thecaphora, as considered here, 
includes those species whose rather firmly united spore-balls con¬ 
sist of reddish-brown spores smooth on the contiguous surfaces 
but variously marked on the free. So far as is known the ger¬ 
mination is by elongated germ tubes that usually produce solitary 
terminal conidia. Sorosporium, with which it has been con¬ 
fused, has spores much like Ustilago and the spore-balls are often 
only temporarily united. Burrillia has been made to include 
those Doassansia-like species that lack a true cortex. 
The writer wishes to express his especial obligation to 
Professors Farlow and Thaxter, of Harvard, for their very great 
help, in many ways, in furthering his study of this group. He 
is also indebted to a considerable number of American and some 
European botanists who have furnished specimens or otherwise 
rendered aid. Specific acknowledgment of such aid will be made 
later. That a wealth of material has been available for exam¬ 
ination is shown by the fact that every species listed from this 
country, except one, has been seen. Type material of all species 
described from North America has been examined. A great 
difficulty in the systematic study of the group is that with such 
an abundance of material one finds, in some cases, such great 
variation that it is often a matter of arbitrary decision as to the 
disposition of certain specimens or even as to the treatment of 
certain species. It is hoped that the minimum of errors of judg¬ 
ment have attended the work in this respect. 
