230 PHYLUM VII. CARPOMYCETEAE 
ground by the rapid growth of a central mass of stalk 
tissue, and later by arupture of tissues the hymenium be- 
comes external. 
386. At maturity the spore fruit of the Mushroom 
consists of a short thick stalk, bearing an expanded um- 
brella-shaped cap, beneath which 
are many thin radiating plates, the 
gills. Each gill is a mass of fila- 
ments whose enlarged end-cells 
(basidia) come to, and completely 
Fra. 111.—Development of Cover, both of its surfaces. The 
ar basidia produce spores in the usual 
manner for plants of this class, that is, upon slender stalks. 
387. In the Pore fungi (Polyporaceae) the basidia line 
the sides of pores; in the Prickly Fungi (Hydnaceae) and 
Coral] fungi (Clavariaceae) they cover the surface of spines 
and branches; while in the Leathery fungi (Thelephora- 
ceae, Stereum, etc.) they form a smooth surface. 
388. Nothing is yet known as to their sexual organs. 
Several botanists have described such supposed organs 
upon the vegetative filaments before the formation of the 
spore fruit, but there are grave doubts as to the correct- 
ness of the observations, and it is the general opinion that 
these organs have become obsolete. 
389. The vegetative filaments (mycelium) of some 
species of this order (as Fomes fomentarius, ete.) often 
form thick, tough, whitish masses of considerable extent 
in trees and logs. 
390. We know but little as to the germination of the 
spores and the subsequent development of the vegetative 
filaments, 
391. Several families of more or less reduced basidium 
fungi which probably have been derived from the fore- 
going families, as the Ear Fungi (Auriculariales), Jelly 
