1916] Yates: Histology of Calif ornian Bohtaceae 253 



poses of comparison with that of our Califoruian forms referred to 

 *S'. Eastivoodeae. 



Histology 



The pileus is covered with a ritul 40 to 50/i, in thickness, made up 

 of dark brown liypliae densely matted together. Beneath this outer 

 layer is a second, 160 to llOfi in thickness. This second layer is lighter 

 in color than the outer and the hyphae composing it are not so closely 

 matted together, though they are somewhat darker and more closely 

 interwoven than are the hyphae of the context. Both layers of the 

 rind and also the context are made up of hyphae 4 to S/x in diameter. 

 The structure of the hymenium is the same in every detail as that of 

 Suillellus Eastivoodeae, Form A, previously described. 



The surface of the stipe is protected by a rind 20 to 'SO/x in thick- 

 ness, consisting of an almost solid tissue formed of very densely com- 

 pacted dark-brown hyphae. The hyphae of the context lie nearly 

 parallel to each other and to the long axis of the stipe. These hyphae, 

 unlike those of most of the other plants I have investigated, are rather 

 dark in color. The hyphae of the context increase from 4/i, in diameter 

 near the rind to as much as 12 to 16/x at the center of the stipe. The 

 hyphae also become lighter in color as the center of the stipe is ap- 

 proached. 



ROSTKOVITES P. Karst 



This is a genus distinguished from Ceriomyces by the presence of 

 granular dots on the stipe and in this connection it may be well to 

 repeat that in Ceriomyces communis, Form B, structures are found on 

 the stipe which resemble the "glands" found in Rostkovites rather 

 closely. This fact would seem to indicate that the presence or absence 

 of glandular dots is merely a matter of their relative size and abund- 

 ance, rather than of their actual presence or absence. Certain species 

 of other genera are described as glandular dotted but these genera are 

 all distinguished from Bostliovites by the presence of an annulus. 

 Moreover, we shall see when we consider Boletus luteus that in this 

 species at least, which is described as possessing glandular dots on the 

 stipe, these dots are quite different in their origin from those in 

 Rostkovites. 



Rostkovites is a siiiali genus comprising four North American 

 species. Of these four species two have been collected in California. 

 Most of the species of Rostkovites grow in the vicinity of coniferous 



