258 University of California Publications in Botany [You 6 



some -i/M in diameter. This layer, together with the hairs and jelly, 

 form a definite surface "skin" which can be readily peeled away from 

 the context. The context of the pileus consists of very densely inter- 

 twined hyphae, 8 to 12/i, in diameter, with thick walls (Ifi) and con- 

 taining granular contents (pi. 24, fig. 23). 



The structure of the hymenium and of the tissue between the tubes 

 resembles the corresponding structures in R. graniilatus except that 

 the glands appear to be less numerous. 



The surface of the stipe is nearly covered with "glands" similar 

 in every respect to those of B. grannlatus. Over the surface which 

 is not occupied by glands there is a differentiated rind formed by 

 slightly swollen tips of hyphae standing in a position perpendicular 

 to the surface. These hyphae are rarely more than 1 or 2/^ in diameter 

 and are brownish in color. The hyphae of the context of the stipe are 

 8 to 12^ in diameter and lie in a position parallel to each other and to 

 the long axis of the stipe. The hyphae increase in their diameter as 

 they approach the center of the stipe, where they may attain a diameter 

 of 16/x,. The hyphae forming the context contain a granular substance 

 (probably an oil). Drops of oil are visible among the hyphae in 

 abundance. 



BOLETUS (Dill.) L 



The genus name Boletus has been retained by ]\Iurrill for the 

 ochraceous or brown-spored species of the Boletaceae which possess 

 an annulus and the top of whose pileus is smooth and viscid. Boletus 

 luteus is the only species of the Boletaceae described by Linnaeus 

 which has an annulus. This species is the type of the genus Boletus 

 as limited by Murrill. 



As limited by Murrill, the genus Boletus includes plants with an 

 annulus and a smooth, viscid pileus. The hymenophore is annual and 

 terrestrial. The context is white or yellowish. The small, angular 

 yellowish tubes are adnate and are covered by a veil. The smooth, 

 yellowish-brown spores are oblong-ellipsoidal or, rarely, globose. The 

 solid stipe is central, often glandular, dotted and annulate. 



Boletus luteus L 



Plate 21, figure 9 

 Dried specimens of certain of our Californian plants were sent to 

 Dr. Murrill, who referred them to Boletus luteus. Based upon the 

 description by Murrill, Boletus luteus may be described as follows: 



