252 University of Calif ornia Publications in Botany \yoi.. 6 



no cj-stidia observed. The tissue between the tubes consists of inter- 

 woven hyaline hyphae -i^u in diameter. 



In neither Form A nor Form B was there noted any histological 

 structure at the mouths of the tubes to which the red color might be 

 ascribed. The red color is probably due to a red pigment in the proto- 

 plasm. 



The stipe has a rind about GO/x in thickness formed by the greatly 

 swollen tips of hyphae standing in a position nearly perpendicular 

 to the surface of the stipe. These swollen hyphal tips are 16 to 20ja in 

 diameter and 30 to ^Ofx in length. They are brownish-yellow in color. 

 Beneath this outer rind there is a tissue (the context) formed of inter- 

 woven hyphae varying in diameter from 2 to 6/x. These hyphae 

 gradually become greater in diameter and less densely interwoven as 

 the center of the stipe is approached. At the center the hyphae are 

 hyaline and 4 to 8/i, in diameter (pi. 22. fig. 14). 



From the above description of the histology of Form B and of 

 Form A it can be seen that the plants referred to these two forms 

 differ from each other not only in details of their morphology but also 

 in the histology of both the surface of the pileus and the surface of 

 the stipe. 



Suillellus Frostii (Russell) ]\lurrill 



This is an Eastern species of Suillellus of which a dried specimen 

 was contributed by Dr. ]\Iurrill. Its histology is described here for 

 the purpose of comparison with the histology of our Californian species 

 of Suillellus. 



Suillellus Frostii is described by ]\lurrill as follows : Pileus convex 

 to plane, gregarious, 6-15 cm. broad ; surface glabrous, shining, viscid 

 in damp weather or when young, blood red. sometimes paler red with 

 patches of yellow ; context firm, juicy, white or yellowish, scarcely 

 changing to greenish blue when wounded, taste mild ; tubes adnate, 

 subdecurrent, depressed, straw yellow within, changing slowly to 

 greenish blue when injured, yellowish brown Mnth age, mouths large, 

 stuffed, edges blood red ; spores oblong-ellipsoid, smooth, brownish 

 yellow, with a greenish tinge when fresh, 12-15 X4-5/a. Stipe subven- 

 tricose, tapering upward, blood red, sometimes with yellow stains, be- 

 coming bluish green when handled, deeply and beautifully alveolate- 

 reticulate its entire length, solid, firm, yellowish within, 7-10X2 cm. 



While this is not a Californian species and I have had to rely upon 

 dried material, an account of the histology is included here for pur- 



