SOME COMMON MUSHROOMS AND HOW TO KNOW THEM 49 



This fungus is of wide distribution and of common occurrence, appearing 

 on logs and trunks. It is easily recognized by the brittle varnished crust of 

 the cap and stem. 



POLYPORUS 



Species belonging to the genus Polyporus present considerable 

 variation in stem, form, and texture. The stem may be central, 

 excentric, or absent; the hymenophore circular, reniform, or hoof 

 shaped, azonate or grooved; and the substance fleshy, soft, corky, 

 or woody. This genus is distinguished from Polystictus by the 

 thicker cap and from Fomes by the nonstratose tubes. 



Species of this genus are widely distributed, and representatives 

 may be found from the extreme North to the Tropics. Polyporus 

 contains a few edible species and many wound parasites, species 

 injurious to economic and ornamental trees. Wound parasites are 

 fungi that gain entrance to the interior of a .tree or host through 

 some unprotected surface resulting from injury by lightning, insect 

 attack, injudicious pruning, or some other agency. 



POLYPORUS BETULINUS. BIRCH POLYPORUS 



In the birch polypore the hymenophore is tough and fleshy, then corky, hoof 

 shaped, umbonate at point of attachment, margin thickened, obtuse incurved, 

 white when young, later light to dark mottled gray, zoneless, smooth ; the 

 pores are minute, short, unequal, whitish. 



The fungus is of common occurrence on birch trees, measuring from 3 to 8 

 inches or more in width. When young it is considered edible, but is tough 

 and possesses a rather strong flavor. It is often used as material for outdoor 

 sketching, for which purpose it is very well adapted. 



POLYPORUS FRONDOSUS 



This species occurs in large tufts, which measure 6 inches to over a foot 

 in breadth. The caps are very numerous, crowded and overlapping, 1 to 

 2 inches in diameter, irregular in shape, curved, repand, lobed or cleft, brown 

 or sooty gray ; the stems are indefinite, branching or confluent ; the pores are 

 very small, white. 



This is a very common plant, growing about stumps, roots, and trunks. It is 

 edible and tender when young, but soon becomes tough. 



POLYPORUS SULPHUREUS. SULPHUR POLYPORUS 



This is a very conspicuous fungus on account of its large clusters and the 

 characteristic sulphur-yellow color. The caps are fleshy, spongy, attached lat- 

 erally, very much imbricated, more or less fan shaped, smooth, even when 

 young, later ridged and furrowed ; margin at first thick and blunt, becoming 

 thinner ; the pores are very small, plane and sulphur yellow. 



Polyporus sulphureus occurs abundantly and is edible, though of doubtful 

 value. It is of interest as a wound parasite on various trees, gaining entrance 

 to the interior of a tree through an exposed surface and finally causing the 

 death of the host. This is a very striking plant on account of the bright sul- 

 phur-yellow color, which quickly attracts the attention of the collector. 



POLYSTICTUS 



Species of the genus Polystictus may be differentiated from those of 

 Polyporus because of being thinner with caps more pliant. None 

 are to be especially recommended for table purposes, but by their 

 abundance and attractiveness they force themselves upon the atten- 

 tion of the amateur or nature student. The species described here 

 are all sessile and shelving. 



