GENERA AND SPECIES. 181 



dark-brown disk. Spores four to six-celled, colorless, 

 spindle-shaped, 16/i, X ^f"- 



3. CoUema myriococcum. Thallus medium, lobes 

 ascending, more or less flexed and folded, surface 

 somewhat granular or warty, dark-blue to black. 

 Apothecia not seen, said to be small, numerous and 

 somewhat immersed. Spores simple, colorless, 

 Ufx X 8/x. 



4. Collema leucopepla. Thallus thin, lying flat upon 

 the substratum, rather indistinctly lobate, wrinkled 

 above and below, often granular ; dark-green above, 

 somewhat paler beneath. Apothecia rather small. 

 Disk reddish-brown, with a translucent whitish tinge. 

 Spores acicular, four to six-septate, 51/a X 3/x. 



5. Collema nigresceiis. Thallus much as in C. leu- 

 copepla. Apothecia small, numerous. Disk flattened 

 to convex, dark-brown. Spores acicular, resembling 

 those of Bacidea, four to six-septate, 35/x X 3yu,. 



6. Collema ryssoleum. Thallus large, thin, lobes 

 ascending ; wrinkled and rugosely folded above, reticu- 

 late below ; dark-green above, somewhat paler beneath. 

 Apothecia small, much as in C. nigrescens. Spores 

 colorless, spindle-shaped, 21/a X 6.5/x. 



7. Collema pulposum. Thallus medium, compara- 

 tively thick, lobes imbricate and somewhat ascending, 

 smooth, margin crenulate ; leek-green to dark. Apo- 

 thecia large, numerous, margin crenate and warty, ex- 

 tending above the concave brown disk. Spores color- 

 less, spindle-shaped to ovoid, elliptical, four to six- 

 celled, rarely multilocular, 21/x X 7.5/x. 



8. Collema laciniatum. Thallus rather small, lobes 



