1916] Yaies: Histology of Californian Boleraceae 229 



general. Levine (1913) in ;i paper on the cytology of the Boleti deals 

 with certain general details of their structure, l)ut in looking through 

 the literature the writer failed to find any description of the histology 

 of any species of the Boletaceae which woiihl aid in the sort of work 

 that it was proposed to carry out. 



The details of the histology of a plant differ, of course, according 

 to the part with which we are working. The structure of the stipe 

 differs from that of the ])ilcus. Furthermore the stipe is differentiated 

 into an interior context and an exterior covering or rind, whose com- 

 parative histology differs very consideral)ly in many of the species. 

 The pileus, exclusive of the hymenium, is also differentiated into the 

 context and a more or less definite rind, with marked differences in the 

 histology of the two parts. The hymenium also has a very definit(^ and 

 characteristic structure. 



The histology of the Boleti is so definitely associated with the de- 

 velopment of the fruiting body that it seems advisable to discuss the 

 early stages in the formation of the complex fruiting body in the 

 Boleti. 



In this connection practically the only literature is summarized in 

 Zeller's (1914) paper, the conclusions of which are confirmed by the 

 small amount of work that I have been able to do on the development 

 of the carpophore, particularly in Rostkovites granulatus. However, 

 it should be stated that I have found a veil present during the early 

 stages of certain individuals of both species of Ceriomyces occurring 

 in the San Francisco Bay region. Zeller's results may be summarized 

 as follows : 



The carpophore, or fruiting body, first appears as a small knob 

 or button on the mycelium. Then this button, at first nearly spherical, 

 begins to elongate and the hyphae in the center arrange themselves 

 parallel to each other and to the long axis of the fruiting body. The 

 hyphae in the peripheral portion are parallel to the surface. At this 

 period there is no visible dift'erentiation of tissue. There then appears 

 a narrow ring of more deeply staining tissue a short distance below 

 the summit and this area gradually broadens. AVhile this is taking 

 place the li\|)hae of the upper pat-t, wliich hitcr Ix'comes the pileus, 

 begin a radial growth and finally give rise to the surface rind. At 

 the same time the hyphae of the deeply staining area grow downward 

 thfiiMgh the deeply staining tissue, which iu)w becomes a plane of 

 cleavage, the hyphae breaking apart in this zone to t'oriii a t'uirow. 

 The hyphae from above the furrow form a palisade layer, which later 



