| Under surface dotted with cyphellae or pseudocyphellae | 1. | Sticta Schreb. |
| Under surface without these organs | 2. | Lobaria Schreb. |
XLIII. Peltigeraceae
A family of heteromerous foliose lichens containing in some instances blue-green (Nostoc), in others bright-green (Protococcaceae) gonidia, and thus representing a transition between these two series. They have large or small lobes and grow on the ground or on trees.
Cephalodia, either ectotrophic (Peltidea) or endotrophic (Solorina), occur in the family and further exemplify the capacity of the fungus hyphae to combine with different types of algae.
The upper surface is a wide cortex of plectenchyma, which in some forms (Nephromium) is continued below. In the non-corticate under surface of Peltigera, the lower hyphae grow out in hairs or rhizinae, very frequently brown in colour. Intercalary growth of the upper tissues stretches the thallus and tears apart the lower under surface so that the hair-bearing areas become a network of veins, with the white exposed medulla between. In Peltigera canina there is further growth and branching of the hyphae in the veins, adding to the bulk of the interlacing ridges.
From all other foliose lichens Peltigeraceae are distinguished by the flat wholly appressed or peltate apothecia without a thalline margin which arise mostly on the upper surface, but in Nephromium on the extreme margin of the under surface, the tip of the fertile lobe in that case is turned back as the apothecium matures, so that the fruit eventually faces the light. In Nephroma has been included Eunephroma with bright-green gonidia and Nephromium with blue-green.
Bitter[1055] has recorded the finding of apothecia on the under surface of Peltigera malacea and not at the margin, as in Nephromium. The plant was otherwise normal and healthy. Solorinella, from Central Europe and Asteristion from Ceylon are monotypic genera with poorly developed thalli.
| Thallus poorly developed. | ||
| Asci 6-8-spored; spores 3-5-septate | 1. | *Asteristion Leight. |
| Asci many-spored; spores 1-septate | 2. | *Solorinella Anzi. |
| Thallus generally well developed. | ||
| Apothecia superficial, sunk in the thallus | 3. | Solorina Ach. |
| Apothecia terminal on upper surface of lobes | 4. | Peltigera Willd. |
| Apothecia terminal on lower surface of lobes | 5. | Nephroma Ach. |
XLIV. Pertusariaceae
Thallus crustaceous, often rather thick and with an amorphous cortex on the upper surface. Algal cells Protococcaceae. Apothecia solitary or several immersed in thalline warts, generally with a narrow opening which barely exposes the disc, and which in one genus, Perforaria, is so small as almost to constitute a perithecium; spores are often very large and with thick walls; some if not all are multinucleate and germinate at many points.