342 Murrill : Polyporaceae of North America 



is therefore a synonym of Mucronoporus and Coltricia. As to the 

 standing of such genera as Hymenochaete and Mucronoporus, based 

 solely on the presence of cystidia, opinion has been divided, but 

 a brief study of various forms will show that this character is pos- 

 sessed exclusively by no one group of fungi and that it varies 

 abundantly even within the limits of a single species. It often 

 affords a convenient clue to the identification of species, but should 

 be accompanied by stronger and more permanent characters in the 

 separation of genera. 



The species of the present genus are terrestrial or wood-loving 

 plants found in dry soil in woods or attached to decayed sticks or 

 roots beneath the ground or growing at times upon much-decayed 

 logs and stumps. Some of the species have a peculiar fondness 

 for places where fires have been built ; others are able to adapt 

 themselves to very varied localities, growing now upon rich soil 

 and again upon dead standing tree-trunks. In appearance, they 

 are usually circular, central-stemmed, brownish plants with rusty 



context and spores and a brown hymenium, which is covered with 

 a yellowish or whitish powder when young. Cystidia are rarely 



present. The consistency of the pileus varies from coriaceous to 



spongy and the surface from concentrically zonate to smooth. 



As to distribution, the members of the genus are about equally 



divided, half of them being cosmopolitan and the other half local. 



The smallest plant of the group is C. cinnamomea, the largest C. 



Memmingeri, a new species known from one locality only. 



Synopsis of the North American species 



1. Pileus concentrically zonate, context thin. 2 - 

 Pileus azonate, context rather thick and spongy. 4- 



2. Pileus shining cinnamon, strigose, striate, thin, flexible, slightly depressed, the mar- 



gin often fimbriate or pseudo-ciliate. I • C. cinnamomea. 



Pileus dull rusty cinnamon to hoary, velvety to glabrous, deeply depressed, the 



margin thicker and less fimbriate. 3- 



3. Tubes small, 0.5 mm. or less in diameter. 2. C. perenms. 

 Tubes large, I mm. in diameter. 3- c - pnrvula 



4. Context homogeneous, hymenium free from spines. 5- 

 Context duplex, soft above and woody below, hymenium beset with spines. 



4. C. tomentosa. 



5. Pileus ferruginous to fulvous, 5 cm. in diameter, surface finely tomentose, stipe 



swollen and soft at the base. 5- C. obesa. 



Pileus darker, fulvous to chocolate-colored, 10 cm. in diameter, surface rough and 



shaggy, stipe scutate and firm at the base. 6- C. Memmingeri. 



