— 2 — 
shaped, with broad, flat lobes on whose edges are borne the apothecia. The 
thallus is covered with a powdery bloom, in color it is a gray green, fre- 
quently turning a reddish brown when pressed. The under surface is 
nearly white, with dark brown felt-like branching veins traversing the sur- 
face of the thallus and growing into a thick mat at the center. 
The apothecia are large, round and flat, and are found on the slightly 
elongated lobes of the upper side of the thallus. The disk is dark brown or 
black, orbicular, the margin thick with finely serrate edges. 
P. venosa is a small, but handsome species; it is rare in the Eastern 
States, but quite common in the far west, grows on wet, clayey, or argil- 
laceous soil, often in the crevices of rocks near waterfalls. 
Peltigera aphthosa 
the center form a close black nap. 
The apothecia are large and round, borne on the ascending lobes of the 
thallus ; when developed they become revolute and curl around these 
extended lobes. 
P. aphthosa is a large and common species, is found on rocks among 
mosses and on the earth. It is easily distinguished from the other Peltigeras 
by the wart-like depressions on the upper side; in some specimens these are 
quite large and crowded, in others they are small and scattered. 
Peltigera horizontalis (L.) Hoffm. This species resembles both P. 
canina and P . polydactyla , but the thallus is smooth, not downy as in P. 
canina , nor polished as in P. polydactyla. The thallus is large, in color 
is greenish to reddish brown. The »under side is about the same color, is 
covered with dark veins which soon coalesce and form a dark brown felt-like 
nap. The fibrils are few and short, and almost black. 
The apothecia are on the scarcely elongated lobes: they are oblong, hori- 
zontal, rather large; the disk is reddish brown, with a finely serrated 
margin. 
P. horizontalis is not so common a species as P. canina and is found in 
the same localities; it is usually fertile. 
(L.)Hoffm. Fig. i. The 
thallus of this species is 
large, smooth, rather 
soft, and covered with 
scattered appressed 
dark, irregularly shaped 
warts. The lobes are 
broad and round. The 
color an apple green 
turning to a dull green ; 
when dried is usually a 
light yellow brown. The 
under surface is cream 
color, with reticulated 
blackish veins, which at 
Fig. i. Peltigera aphthosa X o. 
