ATKINSON: LEPIOTA CRISTATA AND L. SEMINUDA 213 



which ruptures it and forms an internal, annular cavity below 

 the hymenophore primordium. Since the lamellae are later 

 formed in this cavity, as downward projecting salients, it is known 

 as the general annular prelamellar (or gill) cavity. In Lepiota 

 cristata this cavity is not proportionately so large as in Lepiota 

 seminuda described later in this paper. It is weak in the figures 

 3 to 6, but as the palisade area is organized and the gill salients 

 begin to form the annular cavity is more pronounced. It is as 

 broad as the area between the stem and margin of the pileus, 

 but not very deep, as shown in figures 7-17. The epinastic 

 growth of the margin of the pileus lifts the veil up to some extent, 

 thus narrowing the cavity, but in the cases observed the veil is 

 not crowded against the margin of the lamellae, as sometimes 

 occurs in the species of the genus Agaricus (Atkinson, '15). It 

 may very likely occur in certain individuals of Lepiota cristata. 



Origin of the lamellae .—The growth of the pileus margin is 

 centrifugal. The extension of the hymenophore primordium, 

 developed on its under surface is therefore also centrifugal, the 

 older stages being next the stem and the younger ones next the 

 margin of the pileus. As the primordium of the hymenophore 

 ages, the hyphae increase in number by new branches crowding 

 in between the older ones. The hyphae also increase in diameter, 

 becoming parallel and closely packed side by side. Their free 

 ends also come to reach the same level, thus forming an even 

 palisade layer. This begins next the stem and proceeds in a 

 centrifugal manner toward the margin of the pileus, the primordial 

 condition of the hymenophore gradually becoming changed into 

 the palisade condition. 



The lamellae arise as downward growing radial salients of the 

 level palisade. These salients begin next the stem and progress 

 centrifugally toward the margin of the pileus (for details of this 

 process see Atkinson, '15). Figures 7-12 show the origin of 

 the lamellae in one fruit body. The sections from which the 

 photographs were made were selected from a series of sections 

 passing from the middle of the pileus toward its margin. Figure 

 7 is a median longitudinal section, and is therefore nearly or quite 

 parallel with the lamellae. At the left side of the figure the 

 section passes parallel with and through the lamellae, while on 

 the right it passes in a slightly oblique direction. Figure 8 is 



