20 MICROBES, FERMENTS, AND MOULDS. 
TI. Ascomycetes ; Ercot or Rye; Tae MovuLD oF 
LEATHER AND DRIED FRUITS. 
In distinction from the species just described, the 
fungi in this group possess endogenous spores, enclosed 
in a sac or special envelope which is called an ascus ; 
hence the name of the family. Truffles, or Tuberacee, 
are only reproduced by the spores contained in these 
asci; but most of the other ascomycetes present in 
addition several forms of spores, and the phenomenon 
of alternation of generations has led to the belief that 
in this case, as in that of the foregoing group, many of 
the so-called species are only successive transformations 
of one and the same species. This is the case with 
the ergot of rye, a product used in medicine; it is, 
however, a serious and dangerous disease of several 
of our cereals, and particularly of rye (Fig. 8). 
Ergot is caused by a minute parasitic fungus which 
attacks the ear of rye when it is in flower. The 
young flower is covered with a white mass, consisting 
of microscopic spores, formerly termed sphaceliwm 
(Fig. 9). These spores reproduce themselves on other 
flowers, and propagate the evil. 
The mycelium formed by the germination of the 
sphacelium affects the grain, forms in it a thick felt- 
work, and is developed so as to constitute the elongated 
_ substance termed sclerotis (on account of its hardness), 
or ergot; it is called at this stage Claviceps purpurea. 
