454 Vmvcrdty of California Puhlioatwns in Botaniy [^^oi- 7 



but do not in any case constitute a pseudoparenchymatous tissue. The 

 upper layer of the pileus flesh is pigmented brown. 



The lamellar plates extend downward from the pileus (fig. 22, pi. 

 52). They are arranged in pairs; each pair, with the sterile, hairy 

 surfaces together, giving the appearance of a lamella. Each plate, 

 however, is independent of the other to a certain degree, and may 

 varj^ from it in size and shape. A hymenial plate may attain a depth 

 of 3 mm., the depth depending entirely upon the number and length 

 of the growing periods following the origin of the plate, for growth is 

 continuous throughout the duration of favorable conditions. Each 

 plate exhibits a growth region at the margin, which, after the earliest 

 stages, is continuous with and similar to the margin of the pileus. 

 Since the plates arise successively in pairs, a great many different 

 ages and sizes may be found in the same mature sporophore. 



The hymeniuni either covers a much divided single area or is 

 separated into several different areas in the same sporophore, as in 

 plate 53. The elements in the hymenial layer are closely crowded 

 together, and in old specimens tightly adhere to each other, so that 

 a large area of the hymenium may be removed from the subhymenial 

 layer without separating the basidia from one another. 



3. MICROSCOPIC STRUCTURE 



The study of the microscopic structure of Schizophyllum presents 

 considerable difficulty. Upon dehydration the sporophores become 

 hard and brittle, so that the paraffin method of obtaining sections is 

 impracticable. When, by using other methods, sections are obtained, 

 it is found that the hyphal walls are thick, the segments extremely 

 long, and that the nuclei are small and difficult to differentiate by 

 staining. 



The vegetative hyphae commonly branch, but not with great fre- 

 quency. The branching rarely occurs at or near a septum, but usually 

 takes place about the middle of a segment (fig. 1, pi. 54). The hyphae 

 are of two sizes, one having a diameter of 3 to 5/^, and the other being 

 only about 1 or 2ju, wide. The finer hyphae are particularly abundant 

 w^hen the mycelium is grown upon artificial media, but are also found 

 to some extent in wood. The hyphae are often covered with small 

 tubercles, as was described by Brefeld (1889) in S. lohatum and Miss 

 Rumbold (1910) in S. commune. This seems to be a distinctive char- 

 acter. The function of these lateral projections (fig. 2, pi. 54) is not 



