164 HERRE 



Peltigera canina membranacea Tuck. Syn. N. Am. Lich. 1 : 109. 1882. 

 Peltigera canina membranacea Herre, Proc. Wash. Acad. Sci. 7: 374. 

 1906. 



Thallus very thin and papery, becoming greatly expanded, the 

 surface smooth and more or less pitted and furrowed; lobes large, 

 dilated, rounded, irregularly crenate and laciniate, more or less 

 imbricate, often forming mats several layers in thickness; tips of 

 lobes visibly tomentose; color and under surface as in typical form. 



Apothecia numerous, marginal or terminal on somewhat narrowed 

 and extended lobules; spores 48 locular, needle-like, 



^ 



40 - 73i 



Occurring throughout, on mossy tree trunks, rotting logs, and on 

 earth and stones. A European lichen occurring also on the Pacific 

 coast of America and in Mexico. 



PERTUSARIACE^E. 



Thallus uniform crustaceous, attached by the hyphae of the 

 medulla or of the hypothallus, cortex present or absent on the upper 

 side; alga Pleurococcus. 



Apothecia solitary or several immersed in thalline warts, the disk 

 usually very narrow; rarely it is broad and lecanorine in appearance, 

 while in some forms it is pyrenocarpous in appearance; proper mar- 

 gin lacking; paraphyses well developed, usually branched and twin- 

 ing, rarely unbranched and free; spores i8, colorless or brownish, 

 usually very large and thick-walled, simple or bilocular. We have 

 the most important genus of the family, Pertusaria. 



XLII. Pertusaria DC. 

 Pertusaria DC. Fl. Fr. 2 : 139. 1805. 



Thallus as above; apothecia single or more often enclosed in goni- 

 dia-bearing fruiting warts, rarely immersed in the thallus; spores 

 usually large to very large, colorless, rarely dusky or brown, simple, 

 with strongly thickened walls of concentric layers, the inner spore 

 wall smooth or with cross-markings. 



