THE FUNGI 395 
(pileus) portions. The external surface of the cap is covered 
with a layer of asci and paraphyses which together constitute 
the ascigeral layer. To this group belong the Morels and the 
Earth Tongues. 
One of the Morels, Morchella esculenta, is frequently found 
in fire-swept woods. Its fruiting body consists of a hollow, 
externally ridged stipe, bearing upon its summit a fleshy pileus 
whose outer surface is honeycombed with ridges and depressions. 
The depressions are covered with an ascigeral layer composed 
of asci and paraphyses. This species is edible. (See F ig. 
293.) 
ORDER 6.—PYRENOMYCETALES, the mildews and black fungi, 
common as superficial parasites on various parts of plants. To 
the Family Hypocreacee of the black fungi division of this order 
the Ergot fungus, Claviceps purpurea, belongs. 
Lire History or Caviceps PurpureA.—Through the 
agency of winds or insects the spores (ascospores or conidia) of 
this organism are brought to the young ovaries of the rye (Secale 
cereale). They germinate into long filaments called hyphae, 
which, becoming entangled to form a mycelium, spread over the 
ovary, enter it superficially, secrete a ferment, and cause decom- 
position of its tissue and the resultant formation of a yellow, 
mucous substance called honey dew, which surrounds chains of 
moniliform reproductive bodies known as conidia. The honey 
dew attracts certain insects which disseminate the disease to 
other heads of grain. 
The mycelial threads penetrate deeper and deeper into the 
ovary and soon form a dense tissue which gradually consumes the 
entire substance of the ovary and hardens into a purple, some- 
what curved body called a sclerotium, or official ergot—the 
resting stage of the fungus, Claviceps. 
The ergot falls to the ground and in the following spring 
sprouts into several, long stalked, globular heads called stromata 
or ascocarps. Each (fruiting) head or ascocarp has imbedded 
in its surface numerous flask-shaped invaginations called peri- 
theca, from the bases of which several sacs or asci develop from 
the ends of hyphae. Within each ascus are developed eight fili- 
form spores (ascospores) which, when the ascus ruptures, are 
