ATKINSON: LEPIOTA CRISTATA AND L. SEMINUDA 217 



annular zone of new growth on the lower side of the margin of the 

 pileus fundament and is well shown in figure 19. This figure is 

 from a longitudinal, and nearly median, section of a young basidio- 

 carn The hyphae of the hymenophore primordium extend out- 

 ward and downward at an angle of about 45° from the axis of 

 the stem By the introduction of numerous new branches this 

 internal annular zone of new growth is already quite compact 

 and takes a deep stain on account of the abundant protoplasm in 

 the young hyphae. But the lower surface of the hymenophore 

 primordium is still uneven and more or less frazzled or fimbriate, 

 since the slender tapering hyphae in their growth through the 

 ground tissue beneath have not reached the same level and are 

 Ls crowded because of their tapering form. This is well shown 

 in FIGURES 21 and 22, which are from more highly magnified 

 photomicrographs of the hymenophore and adjacent tissue at 



the left side of figure 19. , ., r 1 ^- 



Even at this young stage the margin of the pileus fundament 

 and of the hymenophore shows epinastic growth, ihe trans- 

 section of the hymenophore presents a slightly arched form, 

 convex above, concave below. At the extreme left of the hymeno- 

 phore fundament in figures 21 and 22, the hyphae are more 

 loosely associated, since this portion of the hymenophore is the 

 vounger. This rapid increase in the elements of the hymenophore 

 primordium over that of the ground tissue below produces a 

 pressure which exerts a tension on the loose ground tissue and it 

 is gradually torn apart, forming the general annular, prelamellar 

 cavity. A very early stage in the formation of this cavity is 

 shown in figures 19-22. Figure 20 is from a section through 

 one side of the annular hymenophore primordium parallel with a 

 tangent to its surface and also parallel with the axis of the stem. 

 The uneven, ragged lower surface of the hymenophore at this 

 stage is shown, as well as the early stage of the gill cavity with 

 isolated hyphae or slender loose strands extending across the 



weak cavity. 1 r u -i 



Organization of the level palisade.— Since growth of the pUeus 

 margin and of the hymenophore primordium is centrifugal, the 

 older stage of the hymenophore is next the stem. It is in this 

 region that the primordial stage of the hymenophore first passes 

 over into the level palisade stage by increase in the number of the 



