ORDER AGARICALES 495 



species. The labyrinthiform or lamelloid species like Daedalea and Lenzites 

 may show relationship to the Agaricaceae but they may represent merely 

 a parallel course of development. Some of the genera close to Polyporus 

 have gills radially elongated. 



Order Agaricales. Largely fleshy, but some leathery or even corky or 

 woody at maturity. Basidia usually chiastic (after removal of Cantharellus 

 to the forgoing order). Hymenium on lamellae (gills) or pores (Boleta- 

 ceae), gymnocarpic or pseudoangiocarpic or angiocarpic. Spore fruits 

 mostly stipitate, more often centrally, but sometimes attached laterally 

 or even resupinately, without stipe. Hymenium usually not formed on the 

 edges of the pores or lamellae. The distinction between Polyporales and 

 Agaricales is not always sharp and it is possible that these intergrade so 

 completely that the two groups cannot justifiably remain as distinct 

 orders. 



Family Boletaceae. This family consists of fungi growing on the 

 ground almost exclusively. The spore fruits are fleshy and stipitate, cen- 

 trally so in most species. The pileus is thick and convex and the layer of 

 pores is mostly easily separable from it. The pores are usually easily 

 broken apart from each other. In the genus Ixechinus, described by Heim 

 (1939) from Madagascar, the trama separating the young pores splits so 

 that at maturity they are separate and become divergent with the up- 

 rolling of the pileus. Thus they have a superficial resemblance to Fistulina, 

 but the origin of the separate pores is entirely different. In some genera a 

 veil covers the layer of pores in the young spore fruits, extending from the 

 edge of the pileus to the stipe. The pores in some genera are elongated 

 somewhat in a radial direction, suggesting a transition to or from the 

 Agaricaceae. 



Some species form large spore fruits. Heim (1936) described Boletus 

 (Phlehopus) colossus from Madagascar with a pileus up to 60 cm. broad 

 and 4 to 6 cm. thick, and with a stipe up to 25 cm. tall and 22 cm. thick in 

 the lower swollen basal portion. The whole fungus weighed 6 kg. The flesh 

 of the various species in the family may be mainly white or pink or yellow. 

 In many species it becomes blue or blue-green when bruised, in others re- 

 maining unchanged. Treatment with KOH, NH4OH, and other chemicals 

 brings about various color changes which are of value in the distinction of 

 species and genera. The spores vary from pale to yellowish to purplish or 

 yellow-brown and may be small or above 20/x in length. They may be thin- 

 walled and smooth or may have external ridges, warts or reticulations. In 

 some cases the endospore is covered with prickles which reach into or 

 through the exospore. Germ pores are produced in a few species. Some 

 species are edible and some are known to be poisonous. Boletus edulis Bull, 

 ex Fr., according to Mez (in a verbal communication to the author), con- 

 tains a toxalbumin that when injected into the blood stream is extremely 



