190 REVISION. OF THE Хоктн AMERICAN HYDNACEAE 
pl. 44. f. 2; Gillet, M. 378 * ; Roze et Richon, Atlas des Champ. 
pl. 64. f. 1-5; Vittadini, Desc. dei Fungh. Mang. pl. 26. f. 1—3. 
Exicc. : Roumeguére, Fung. Select. 5602; Rabenhorst-Wint. 
Fung. Europ. 3641 +; Kellerman, Ohio Fung. 127. 
If any species of this genus can be said to be more variable 
than any other that distinction belongs to Ё, Erimaceus. Yet it 
appears to be impossible to group the variations into species with- 
out making almost as many species as one finds specimens. The 
typical form of this plant is as described above. From this type 
form the plant varies extremely in almost every feature. The 
whole mass may be globose with a scarcely evident point of attach- 
ment or it may be strongly vertically compressed and broadened 
until the plant appears almost ungulate or dimidiate ; it may be 
narrowed behind into a comparatively slender stipe, or it may be 
sessile ; it may be horizontal, pendent, or with the upper portion 
of the tubercle ascendant; the tubercle may be lobed suggesting 
an approach to Z. caput-ursi, or at the base of the teeth it may be 
irregularly perforate and obscurely branched, it may be perforate 
throughout, or finally may consist of a mass of anastomosing 
branches; the teeth may be long or short,t straight, curved, or 
flexuose, terete or flattened ; the flesh may be soft, tough, or, at 
least when dried, flaky and brittle ; the upper surface may be 
sparsely fibrillose, or it may be covered densely with long flex- 
uose spore-bearing fibrils, or with short erect stiff processes, also 
spore-bearing. Forms characterized by the last named feature 
have usually been referred to Ё. Caput-Medusae. But the feature 
thus emphasized as a specific character appears to be only a more 
vigorous development of the normally sparse fibrils of the typical 
H. Erinaceus, even in the matter of bearing spores. Moreover, 
even these forms do not strictly correspond to the description and 
figure of H. Caput-Medusae Bull. Тһе last named species does 
not appear to have been found in this country. 
H. Erinaceus is found most commonly emerging from wounds 
in living oaks, often from holes made by woodpeckers ; occasion- 
* Numbered according to the ** Liste” of the Author. gus 
t The specimen, however, is from Perryville, Missouri, 
I have seen specimens in which the longest tooth was not over 5 mm. long and 
others in which the longest tooth was fully 30 mm. in length, 
