426 Murrill : Polyporaceae of North America 



which soon ceases to grow at the center, while the hyaline 

 borders continue to grow upward and form a cup resembling spe- 

 cies of Nidularia. The margin of the cup is thin and entire or 

 undulate and becomes darker like the center when the limit of 

 growth is reached, while the concentric zones within very plainly 

 show the progress of the development. The cup varies from 

 deeply infundibuliform to shallow or even flat at times and the 

 central portion which has ceased to grow is much cracked radially 

 to accommodate itself to the growing exterior. 



The pileus proper usually arises from one side of the cup near 

 its base and expands laterally into a reniform, zonate hymeno- 

 phore considerably larger than the sterile portion. At times the 

 pileus does not develop beyond the surface of the cup and at 

 other times a developed pileus becomes proliferous at several 

 points and give rise to new sterile and fertile portions. Since the 

 formation of the cups continues throughout the growing season, 

 many are overtaken by winter and are found among the new ones 

 the following spring. The old pilei rarely remain over winter, 

 being fragile and readily devoured by insect larvae. 



Poronidulus conchifer (Schw.) 



Boletus conchifer Schw. Syn. Fung. Car. 72. 181 8. 

 Boletus virgineus Schw. Syn. Fung. Car. 72. 18 18. 



This species was first described from North Carolina, but it is 

 known to be common in many parts of North America on fallen 

 branches and dead limbs of the elm, its only host. Under the 

 first name Schweinitz described forms that showed the cups at- 

 tached to the developing pilei ; under the second he placed fully 

 developed fruit bodies showing little trace of the sterile part from 

 which they sprang. The plant is confined to North America. 

 Among collections examined are the following : Massachusetts, 

 King; Connecticut, U liitc ; New Hampshire, Minns ; New York, 

 Earle, Murrill; New Jersey, Baric, Murrill; Ohio, Lloyd; Vir- 

 ginia, Murrill ; Alabama, Baric ; Kansas, Bartholomew. 



