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244 University of California Publications in Botany [Vol. 6 



and size of the tubes. In this plant the mouths of the pores are at 

 least three times the diameter of those of our Californian plants and 

 are also widely separated from each other, while in the Californian 

 plants the pores are very close together. 



Histology 



Under the microscope the surface of the pileus is seen to be covered 

 by a rind similar in every way to that of C. crassus Form A described 

 below (pi. 22, fig. 11). 



The structure of the hymenium is also the same as in that of 

 Form A. 



The stipe is covered by a rind 20 to SO/x in thickness, formed of 

 a tangled mass of delicate hyphae 1 to 2ju, in diameter, arising as 

 branches from the hyphae of the context (pi. 22, fig. 13). The con- 

 text of the stipe consists of somewhat interwoven hyphae 4 to 6/a in 

 diameter. While branched and interwoven to a considerable degree of 

 complexity, the hyphae of the context always maintain a general 

 position parallel to the long axis of the stipe. 



Ceriomyces crassus, Form A 



Plate 22, figure 12 



This is the most common form occurring in this region which 

 has been referred to Ceriomyces crassus by Murrill. The plants are 

 medium-sized, the pileus being 5 to 7 cm. broad, while the stipe is 

 5 to 6 cm. in length and 1.0 to 1.5 cm. in diameter. The surface of 

 the pileus is convex or sub-hemispherical, reddish in color and dry. The 

 context of the pileus is 8 to 10 mm. thick, white and turning to a 

 faint pink when cut and then returning slowly to the original color. 

 The tubes are 5 to 6 mm. long, white, not changing to blue, and stuffed 

 when young, mouths small (4 to 5 to a mm.) and circular. Spores 

 smooth, yellowish brown, 14 to 16 by 4 to S^n. The surface of the 

 stipe is a dirty white, somewhat roughened but not at all reticulate. 

 The stipe is slightly enlarged below. Context white and changing as 

 does the flesh of pileus. All parts of the j^lant turn blue when attacked 

 by insects but there is no change in color when the flesh is cut with 

 a knife. 



Form A differs from the description of Ceriomyces crassus in the 

 following details. The flesh turns a faint pink when exposed to the 

 air and then slowly regains its original color. The tubes are white. 



