464 COMPARATIVE MORPHOLOGY OF FUNGI 



In their present provisional limits the Paxillaceae ascend from 

 resupinate to infundibuliform and finally Agaricaceous, apparently 

 gymnocarpous fructifications. Their flesh is firm; the lamellae are 

 decurrent and membranous. Some species are used for food. 



Boletaceae. — The fructifications are always pileate, and centrally 

 stipitate. The tube layer is easily separable from the flesh of the pileus. 

 Many species contain fat reservoirs in special hyphae from which on 

 injury flows a colorless fluid which colors intensely in air. The basidia 

 correspond to the usual four-spored type. The young nucleus in all 

 species so far studied passes through its usual division shortly after its 

 entrance (Levine, 1913). 



In Boletus Zelleri (Ceriomyces Zelleri) (Zeller, 1914) and Boletus 

 parasiticus (Kuehner, 1926) development is gymnocarpous. In Boletus 

 flavus (Ixocomus flavus) and Boletinus cavipes the annular furrow is at 

 first on the surface then in the young stage, the hyphal tissue of the 

 margin of the pileus is continued in a more or less definite partial veil 

 to the rind of the stipe and the tubes and the hymenium arise with an 

 arched annular cavity. Basidia and spores are produced in a hymenium 

 which covers the top of the annular furrow before the tubes are formed, 

 as in the Polyporales (Kuehner, 1926, 1927a). In most species the 

 remains of the veil disappear in the course of development so that the 

 mature condition is no longer reminiscent of the pseudohemiangiocarpous 

 young stage. In others in which it is strongly formed, as in Boletinus 

 cavipes and Strobilomyces, remnants remain on the stipe as a ring, or on 

 the margin of the pileus as a cortina. In still others, unfortunately 

 imperfectly known genera, e.g., in Volvoboletus, a universal veil is differ- 

 entiated as in the Amaniteae in the formation of the fructification. 



All these characters raise the Boletaceae above the Polyporales in 

 which they were usually placed and place them among the Agaricales. 

 These relationships are reinforced in that the Boletaceae also histolog- 

 ically stand considerably higher than the Polyporales and here again 

 have attained the stage of the Agaricales (Yates, 1916). 



Patouillard (1900) and Maire (1902) — who have been followed in 

 this book — advocated that the Boletaceae should be connected to the 

 Paxillaceae, in the Agaricales, where the tramal layer also is easily 

 loosened from the flesh of the pileus. This removal indicates a further 

 step in the recognition that the lamellae and tubiform tramal plates are of 

 secondary importance in a systematic treatment of the Basidiomycetes, 

 and that a natural classification of this order can be completed only with 

 histological and cytological characters. 



Many species are edible. 



As an appendix to the Agaricales, Rhacophyllus lilacinus on dead wood 

 in the tropics should be considered, since it undoubtedly has affinities 

 with this family, although its ontogeny and cytology are only partially 



