496 CLASS BASIDIOMYCETEAE 



poisonous but whose toxic character is destroyed in the process of diges- 

 tion when the fungus is eaten. 



The spore fruits of various members of the family have been studied as 

 to their ontogeny by Kiihner (1927), Elrod and Snell (1940), and others. 

 In some cases they are entirely gymnocarpic, i.e., as they develop they are 

 more or less cylindrical and then at the top the hyphae spread outward to 

 form the pileus. The basidia begin to appear and to bear spores along the 

 stipe, especially the upper portion, and the under side of the pileus, before 

 the pores begin to develop. They may even be formed on the upper surface 

 of the pileus. The enlarging pileus curves downward at the margin as the 

 pores develop but in the truly gymnocarpic forms never curves inward so 

 far as to come into contact with the stipe. In the pseudoangiocarpic 

 species the development is like the foregoing except that the edge of the 

 pileus eventually comes into contact with the stipe, forming a circular en- 

 closed chamber lined above by the developing pores and centrally by the 

 stipe. The marginal tissues of the pileus and the portion of the stipe with 

 which they join may enlarge as the pileus grows in diameter and flattens 

 out, so as to produce an annulus which in Paragyrodon sphaerosporus (Pk.) 

 Sing. {Boletus sphaerosporus Pk.) spreads from near the base of the stipe 

 to the margin of the mature pileus as a grayish-white sheet up to 6 or more 

 cm. broad, leaving a chamber between it and the pore layer. Whether an 

 annulus is formed or not the enlargement and flattening out of the pileus 

 eventually exposes the pores to the air so that the spores may be carried 

 away by air currents. It is doubtful whether true angiocarpy occurs in this 

 family, i.e., development of the pores in a cavity formed internally in the 

 spore fruit and not by the curving downward and inward of the pileus 

 margin. In the genus Gastroboletus the surface layer of the pileus and 

 stipe remain connected and include the young hymenophore like a perid- 

 ium. Here, as in Paragyrodon sphaerosporus, the development is probably 

 pseudoangiocarpic. 



The several hundred species here included in one family were divided 

 by Singer (1936) into two famihes, Boletaceae and Strobilomycetaceae 

 with a total of 21 genera, to which (1945-1947) he added three other 

 families, Gomphidiaceae, Paxillaceae and Jugasporaceae, usually placed 

 in the old family Agaricaceae. These five families then form his Suborder 

 Boletineae. Coker and Beers (1943), on the other hand, recognize only 

 three genera of Boletaceae in the usual sense, in North Carolina. Murrill 

 (1910) recognizes 11 genera in North America. 



It has long been recognized that the genus Paxillus of the old family 

 Agaricaceae has many points of similarity to the Boletaceae: frequent oc- 

 currence of ti-ansverse ridges between the lamellae, ease of separation of 

 the lamellae from the pilear trama, gymnocarpic development of the spore 

 fruit and certain cytological and chemical similarities. Whether these 



