460 Umiuersittf of California Publioaitiorns in Botany [Vol. 7 



which surface constitutes the hymenium primordium. This is exactly 

 as described by Hasselbring (1907), but he did not go into detail 

 concerning the placement or development of the hymenial plates. 

 The pore attains a width of from 1.5 to 2 mm. before the appearance 

 of the first pair of plates. Dozens of specimens in the ' ' apical depres- 

 sion" or "peziza" stage have been observed where there was no indi- 

 cation of lamellae. By splitting the specimen in half longitudinally 

 the entire surface of the hymenium primordium may be examined 

 with a hand lens. Microscopical examination of prepared sections 

 fails to disclose any indication of closed chambers or of " gills ' ' before 

 the "lamellae" are plainly visible upon the surface of the hymenium 

 primordium. 



The placement of the "gills" may be easily observed in actively 

 growing moist specimens (figs. 4^14, pi. 52). They arise as short, 

 isolated ridges upon the surface of the hymenium primordium. The 

 primary ridges arise successively from a point beneath the attachment 

 of the stipe, and grow outward in a radial direction until they finally 

 unite with the edge of the pileus. The secondary "gills" originate 

 between the gills already developed, but do not extend so near to the 

 stipe as do those already formed. They occupy, as BuUer (1909) 

 noted, an isolated, subterminal position within the interlamellar space 

 in which they have been formed. As growth proceeds, however, the 

 distal ends gradually approach the pileus margin and eventually unite 

 with it, as do the primary ridges. 



Soon after a "gill" unites with the pileus margin, the pileus 

 becomes split in from the edge, though often this is not disclosed 

 upon the dorsal surface because of the hyphal covering. This mar- 

 ginal splitting is doubtless to some extent hygroscopic, as specimens 

 kept moist from the first are split only slightly, while those subjected 

 to alternate wetting and drying are split farther toward the stipe ends 

 of the "gills," dividing the pileus as well as the hymenium into narrow 

 finger-like projections, the crenatures of BuUer (1909). 



Occasionally there is an unusual placement of certain "gills." 

 Sometimes they arise at an angle to the radial direction. In this case 

 they frequently remain short and isolated. Often there is a consider- 

 able sterile area between the two hymenial plates (fig. 1, pi. 60). This 

 is very commonly found at the stipe end of "gills" in lateral sporo- 

 phbres. Rarely the first few primary gills formed unite with each 

 other and the pileus margin to divide the hymenium primordium into 

 several separate areas, in which the secondary "gills" later are formed 

 (fig. 15, pi. 52). 



