Lichens

by Annie Lorrain Smith

Spores simple, colourless, globose or ellipsoid	1.	*Heppia Naeg.
Spores muriform, colourless, ellipsoid	2.	*Amphidium[1054] Nyl.

XLI. Pannariaceae

The members of this family are also non-gelatinous, though for the most part associated with blue-green gelatinous algae, Nostoc or Scytonema. The gonidia are bright-green in the genera Psoroma and Psoromaria, the former often included under Lecanora, but too closely resembling Pannaria to be dissociated from that genus.

The thallus varies from being crustaceous to squamulose or foliose, and has a cortex of plectenchyma on the upper and sometimes also on the lower surface. The apothecia are superficial or lateral and with or without a thalline margin (lecanorine or biatorine), the spores are colourless.

Zahlbruckner has included Hydrothyria in this family. It is a monotypic aquatic genus found in North America and very closely allied to Peltigera. The British species of the genus, familiarly known as Coccocarpia, have been placed under Parmeliella, the former name being restricted to the tropical or subtropical species first assigned to Coccocarpia and distinguished by the cortex, the hyphae forming it lying parallel with the surface though forming a regular plectenchyma.

An Antarctic lichen Thelidea corrugata with Palmella gonidia is doubtfully included: the thallus is foliose, the apothecia biatorine with colourless 1-septate spores.

Thallus with bright-green gonidia.
With Palmella	1.	*Thelidea Hue.
With Protococcaceae.
Apothecia non-marginate (biatorine)	2.	*Psoromaria Nyl.
Apothecia marginate	3.	Psoroma Nyl.
Thallus with Scytonema gonidia.
Apothecia marginate, spores 1-septate	4.	Massalongia Koerb.
Apothecia non-marginate; spores simple.
Upper surface smooth	5.	*Coccocarpia Pers.
Upper surface felted	6.	*Erioderma Fée.
Thallus with Nostoc gonidia.
Apothecia marginate; spores simple	7.	Pannaria Del.
Apothecia non-marginate; spores various.
Thallus crustaceous or minutely squamulose	8.	Placynthium Ach.
Thallus squamulose, cortex indistinct	9.	*Lepidocollema Wain.
Thallus squamulose or foliose, cortex cellular	10.	Parmeliella Müll.-Arg.
Thallus foliose, thin veined below	11.	*Hydrothyria Russ.

XLII. Stictaceae

Thallus foliose, mostly horizontal, with a plectenchymatous cortex on both surfaces, a tomentum of hair-like hyphae taking the place of rhizinae on the lower surface. Algal cells Protococcaceae or Nostoc. Cephalodia and cyphellae or pseudocyphellae often present. Apothecia superficial or lateral; spores colourless or brown, variously septate.

The highly organized cortex and the presence of aeration organs—cyphellae or pseudocyphellae—which are almost solely confined to the genus Sticta give this family a high position as regards vegetative development. The two genera are of wide distribution, but Sticta is more abundant in the Southern Hemisphere. Lobaria pulmonaria is one of our largest lichens.