2IO 



in association with the layer just described ; these consist of parallel 

 hyphae extending in the direction of growth and are comparable to 

 the "veins" in the lower surface of the thallus of Hydrothyria ve- 

 nosa. 



The apothecia are large, orbicular and occur on the margin of 

 the thallus-lobes. They are immersed in the thallus so that the 

 large flat disk is scarcely raised above the surface. This is a mark- 

 ed contrast to the apothecia of the Parmelias and the majority of fo- 

 liose lichens, reminding one somewhat of the apothecia of Heffiia. 

 The epithecium and upper ends of the paraphyses are brown ; the 

 hypothecium is colorless and non-cortical in structure, nor is it separ- 

 able into layers. The paraphyses are colorless and simple. The 

 spore-sacs are of medium size, cylindrical, with the upper portion of 

 the cell-wall considerably gelatinized ; at the upper end occurs a 

 projecting cone of firm lichen cellulose to which the ends of the 

 spores adhere. 



The spores are acicular, colorless and three to five-septate, us- 

 ually slightly curved. 



The range of the species is northern, though some of them ex- 

 tend far south. A large per cent, of the known species occur in the 

 territory, particularly in the mountainous regions ; they grow most 

 commonly upon moss, but also upon soil, rocks and trees. 



PLATE 72. 

 Peltigera canina (L.) Hoffm. 



1. Plant natural size. 



2. Section of apothecium. 



3. Section of thallus. 



4. Paraphysis and spore-sac. 



5. Spores. 



10. Solorina Ach. Lich. Univ. 27. 1810. 



This group, which is represented by only a few species, is very 

 interesting from several standpoints. It resembles the preceding 

 genus in the total absence of a lower cortical layer and in its^apothe- 

 cial characters, but in other respects it is markedly different. 



As a rule the thallus is considerably smaller than in Peltigera,. 

 but is, however, thicker, and shows higher structural differentiations, 

 as we shall presently see ; it is loosely attached to the substratum 



