ORDER AGARICALES 497 



justify transferring Paxillus to the Boletineae, as Singer does, or indicate 

 the close relationship of the latter group to the Agaricaceae is more a 

 matter of opinion. In this hookPaxillus will be retained in the Agaricaceae. 



The Boletaceae are found in the temperate, subtropical and tropical 

 regions of both hemispheres, but especially where the rainfall is fairly 

 abundant or in the season of the year when considerable rain falls. They 

 do not occur in arid regions. Many, perhaps most, of them occur in con- 

 nection with mycorrhizal development on roots of mostly woody plants. 

 Some are confined to the roots of conifers and some of this group are 

 limited to certain genera (e.g., Larix, Pinus, etc.). Gyrodon merulioides 

 (Schw.) Sing. {Boletinus porosus (Berk.) Pk.) is known only in proximity 

 to trees of ash {Fraxinus) and Paragyrodon sphaerosporus (Pk.) Sing. 

 {Boletus sphaerosporus Pk.) only near species of oak (Quercus), etc. 



Among the larger and commoner species several may be mentioned. 

 Boletus edulis Bull, ex Fr. has a reddish brown pileus, white or yellowish 

 within, the flesh not becoming blue upon wounding. The pores are yellow- 

 ish and become greenish with age. The stipe is reticulately marked. The 

 pileus is 6 to 20 cm. broad and 2 to 4 cm. thick and the stipe cylindrical or 

 enlarged below and 5 to 10 cm. tall and 3 to 4 cm. thick. The spores are 

 yellowish to ochraceous brown. The flesh has a pleasant nutty taste. This 

 highly prized edible species occurs in frondose woods. The species related 

 to Boletus luridus Schaeff. ex Fr. (Suillellus luridus (Schaeff.) Murr.) are 

 often about the same size as the foregoing and the pileus has much the same 

 appearance above. The flesh is whitish or yellowish but becomes blue very 

 rapidly when exposed to the air. The pores are yellowish with red mouths. 

 The stipes are 5 to 10 cm. tall and 1 to 2 cm. thick, reddish below, yellow 

 above, reticulated near the top. This species is reputed to be poisonous. 

 Tylopilus felleus (Bull, ex Fr.) Karst. (Boletus felleus), also may be con- 

 fused by a beginner with both the foregoing. It differs in its pink spores, 

 its white flesh, which may turn pink on wounding, and its intensely bitter 

 taste. The pores, which are white, become flesh colored as the spores are 

 produced in large numbers. The stipe may be reticulate above or com- 

 pletely reticulate. All three species may be found in the same woods. 

 Suillus luteus (L. ex Fr.) S. F. Gray grows in the vicinity of species of pine. 

 The yellowish to reddish brown pileus is very viscid. The flesh is pale yellow- 

 ish, not changing color when wounded. The stipe is pale yellow to reddish 

 brown and glandular dotted, and has a large persistent annulus. It is edible. 

 Strobilomyces floccopus (Vahl ex Fr.) Karst. (S. strobilaceus (Scop, ex Fr.) 

 Berk.) has dark spores, completely covered by a network and with a dis- 

 tinct germ pore. The pileus and stipe are gray when young but the numer- 

 ous shaggy scales quickly become dark. The gray to white pores become 

 reddish or black on wounding or bruising, and are more or less lamellar 

 near the stipe, which has an annulus. This edible species grows in frondose 



