STRUCTURE, 55 
form particular, often tun-like or globular cells; the longer ones 
are changed, through the formation of cross partitions, into 
chains of similar cells; the latter often attain by degrees strong, 
thick walls, and their greasy contents often pass into innumerable 
drops of a very regular globular form and of equal size. Similar 
appearances show themselves after the sowing of spores, which 
are capable of germinating in the medium already described, 
from which the air is excluded. Hither short germinating 
utricles shoot forth, which soon form themselves into rows of 
gemmules, or the spores swell to large round bladders filled 
with protoplasm, and shoot forth on various parts of their 
surface innumerable protuberances, which, fixing themselves 
with a narrow basis, soon become round vesiculate cells, and on 
which the same sprouts which caused their production are re- 
peated, formations which remind us of the fungus of fermenta- 
tion called globular yeast. Among all the known forms of 
gemmules we find a variety which are intermediate, all of which 
show, when brought into a normal condition of development, 
the same proportion, and the same germination, as those we first 
described. 
We have detailed rather at length the structure and develop- 
ment of one of the most common of the Mucors, which will 
serve as an illustration of the order. Other distinctions there 
may be which are of more interest as defining the limits of 
genera, except such as may be noticed when we come to write 
more specially of reproduction. 
Ascomycetes.—Passing now to the Ascomycetes, which are 
especially rich in genera and species, we must first, and but super- 
ficially, allude to Tuberacet, an order of sporidiiferous fungi of 
subterranean habit, and rather peculiar structure.* In this order 
an external stratum of cells forms a kind of perithecium, which 
is more or less developed in different genera. This encloses the 
hymenium, which is sinuous, contorted, and twisted, often forming 
lacune. The hymenium in some genera consists of elongated, 
nearly cylindrical asci, enclosing a definite number of sporidia; 
in the true truffles and their immediate allies, the asci are broad 
* Vittadini, “ Monographia Tuberacearum,” 1831. 
