336 SYSTEMATIC 



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 Mull.-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 develop- 

 ment. The two genera are of wide distribution, but Sticta is more abundant 

 in the Southern Hemisphere. Lobaria pulmonaria is one of our largest 

 lichens. 



Under surface dotted with cyphellae or pseudo-] 



, .. Sticta Schreb. 

 cyphellae J 



Under surface without these organs 2. Lobaria Schreb. 



XLII I. 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 (Nephromiwri) 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 Pdtigera 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 Nepkromium on the extreme 

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