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Pl.cellaph. 3. HOMOTHALAME^. 395
A. Thallus gelatinous, when dry cartilaginous; Collematidese.
Thallus crustlike, slightly figured or
uniform
Placynthium. 80.
Thallus pleated tile-wise, roundish;
lohes minute, thick, turgid Enchylium. 81
Thallus rather leaflike, irregular
loles thick, naked, turgid Scytenium. 82.
Thallus leaflike
loles rounded, downy beneath Mallotium. 83.
Thallus leaflike ; lobes naked,
rather membranaceous, blackish green Lathagrium. 84.
Thalbis leaflike; loles naked,
membranaceous, greyish Leptogium. 85.
Thallus very finely torn and
branched Polychidium. 86.
B. Thallus with ajihrous axis, bark crustUke. Usneadeag.
Apothecia shieldlike, terminal, edgeless .... Usnea. 87.
C. Thallus cartilaginous, inside tow-like. Ramalinidese.
Apothecia shicldlike, terminal, nearly
marginless Cornicularia. 88.
Apothecia saucerlike, edged, slightly
pedicelled; thallus nearly solid Ramalina. 89.
Apothecia saucerlike, edged, not
pedicelled; thallus rather pipey Alectoria. 90.
A. CoLLEMATiDEJB. Tkallus entirely gelatinous, homogeneous;
when dry hard, cartilaginous, crustlike, leaflike,
or branched ; apothecia shieldlike, sessile or sHghtly pedicelled,
sometimes when dry coloured in the centre. These
ought to be moistened before they are examined, as many
of them have their apothecia of a different colour when
dry.
I. 80. PLACYNTHIUM. Acharius. Placynthe.
Thallus crustlike, slightly irregular or uniform.
Placynthium nigrum. Black placynthe.
Thallus crustlike, nearly orbicular, broM-n-bhick ; marginal
lobes deeply crenate; central lobes seedHke, slightly
branched ; apothecia at length convex, black, edged.