INTRODUCTION. 
XXI 
There is a fourth family, which includes the subterranean 
species, or Hymenogastracece, but these, as yet, are so poorly 
represented that no synoptical key is necessary. 
The Ascomycetes are a large order of Fungi which derive their 
name from the spores, or sporidia, being developed enclosed in 
globose, clavate, or cylindrical sacs of delicate membrane, 
termed asci. These asci are usually packed closely together 
side by side, so as to form the hymenium, which is either con- 
cealed within a closed receptacle, as in the Pyrenomycetes, or 
becomes exposed, as a more or less concave disc, in the Dis- 
comycetes. These are the two grand divisions of the Ascomycetes, 
the Tuberacece being a smaller group containing subterranean 
species, analogous to the subterranean species of Qastromycetes, 
but having the sporidia produced in asci. At present these 
are too incompletely represented for it to serve any useful 
purpose to remark upon the relations of the genera. It may, 
however, be well to refer here to the two groups at the latter 
part of the volume which are associated together under the 
term “ Imperfect Fungi.” These are the Splueropsideai and the 
Syphomycetece. The former are typically so closely resembling 
the Pyrenomycetes in habit and appearance that they may be 
mistaken for them unless examined with the microscope, when 
it is found that the spores within the perithecia are not pro- 
duced in asci, but at the tips of short sporophores, or spore 
bearers. Some of the species have been traced to an associa- 
tion with certain species of the Pyrenomycetes , as imperfect 
stages, or as pycnidia, or stylospores, but what is their special 
function is yet undetermined ; some of them may prove to be 
autonomous, but it is doubtful if many of them can be so 
ennobled. As for the Hyphomycetes, or moulds, many of them 
are believed to be the conidia of Pyrenomycetes ; such relations 
subsist between many of the species of Isaria and Cordyceps, 
between Tubercularia and Nectria, between Oidium and Erysiphe, 
etc. It may be found hereafter that such destructive genera 
as Cercospora, Fusicladium, and some others have no such 
relationship, but nothing can be affirmed. It is prudent, for 
the present, to regard them as imperfectly known, or, as we 
have called them, “imperfect fungi.” 
The Hypodermem include the fungi parasitic on living plants, 
known as IJstilagines, or smuts and bunts, and the Uredines, 
or rusts and brands. What we have to explain of the former 
Oiay be put in a tabular form. 
USTILAGINEA5. 
Spores simple, soon free. 
At first botryoid. 
Spores smooth or warted . 
Spores mostly areolate 
Always solitary. 
With columella .... 
Without columella. 
1. Ustilago. 
2. Tilletia. 
4. Sphacelotheca. 
