88 
MORPHOLOGY 
Hydnaceae. These are the tooth fungi, so named because the hy- 
menium covers toothlike or spinelike processes. In simpler forms 
the sporophore resembles an incrustation, in which case the teeth are 
on the upper surface. In other cases the teeth occur on the under sur- 
face of a bracket-like sporophore ; while in Hydnum they are upon the 
under surface of the pileus of a mushroom-like sporophore. 
Polyporaceae. These are the pore fungi, so named because the 
hymenium lines tubes that terminate on the surface with porelike 
openings. The sporophores may be incrustations, with pores on the 
upper surface ; or bracket forms (as Polyporus), with pores on the under 
surface; or mushroom-like forms (Boletus), with pores on the under 
surface of the pileus. The incrusting forms and the hard, gray, 
hoof-shaped bracket forms are very common on tree trunks, fallen logs, 
stumps, etc. Many are destructive to trees, the mycelium spreading 
extensively under the bark and through the wood. 
Agaricaceae. These are the gill fungi, being the common mush- 
rooms and toadstools, and the largest family of fleshy fungi. There are 
bracket forms, but the prevailing type 
of sporophore is the mushroom, with 
stipe and pileus (figs. 198, 199); and 
in every case the hymenium covers 
bladelike plates, which are the gills 
(figs. 200, 201). Many of the Agari- 
caceae also are destructive parasites 
on trees, the mycelium penetrating 
the host extensively. 
The development of the character- 
young sporophores; 199, longitudinal istic sporophore is as follows. The 
section, showing relation of stipe and sma ll buttons consist of interwoven hy- 
phae. Soon the rudiments of stalk 
and pileus appear inclosed in a loosely woven envelope (yolva). The 
elongation of the stipe ruptures the volva, whose torn remnant may 
form a ring or sheath about the base of the stipe. In many cases a 
membrane (velum) of hyphal tissue extends in the young sporophore 
from the margin of the pileus to the stipe, covering the gills. When 
the velum is ruptured by the growth of the pileus, it may remain as a 
ring of tissue (annulus) about the stipe (fig. 197). 
The presence of two nuclei in the young basidium, the nuclear fusion, the two 
successive divisions, the migration of the four nuclei into the four sterigmata and 
199 
FIGS. 198, 199. - Coprinus: 198, 
habit, showing stipe and pileus, and 
