2l8 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



hyphal branches, by their increase in diameter, and by the free 

 ends of the hyphae reaching the same level. This stage is well 

 shown in FIGURES 23 and 24 from a slightly older basidiocarp. 

 The general plane of the under surface of the hymenophore rises 

 at a strong oblique angle from the stem, but epinasty of the pileus 

 is curving the margin downwards. In figure 24 the axis of the 

 stem is at the right. The palisade condition of the older portion 

 of the hymenophore, i. e., the portion at the right, near the stem, 

 is well shown. The free ends of the hyphae now register and 

 form an even, or "level," surface. The younger portion, at the 

 extreme left, is still in the primordial stage as shown by the more 

 slender hyphae and the unregistered position of their free ends. 



Figure 25 is from a "tangential" section of the same basidio- 

 carp. This palisade stage of the hymenophore is shown over the 

 middle area which is not far from the stem, while on either side, 

 farther away from the stem, the hymenophore is still in the pri- 

 mordial stage. In older^ basidiocarps, represented by "tangen- 

 tial" sections in figures 27-31, the level palisade is shown to be 

 well established prior to the origin of the gill salients. Figure 26 

 is from the same fruit body, but is from a median longitudinal 

 section, and thus being parallel with the direction of the young 

 lamellae, one cannot determine with certainty whether or not 

 the fundaments of the lamellae have begun their appearance. 

 None are evident on one side of the basidiocarp shown in figures 

 2-] and 28, nor on the left side of figures 29 and 30 from the 

 opposite side. 



The annular prelamellar cavity. — The general annular, pre- 

 lamellar cavity is large and well formed in Lepiota seminuda before 

 the lamellae begin their development. The formation of the 

 cavity begins early by tension on the ground tissue underneath 

 the expanding hymenophore primordium. It rapidly enlarges 

 with increased growth of the hymenophore and pileus, so that on 

 transsection it is circular or elongate, as shown in figures 23, 26, 

 and 32, or broadly elliptical in "tangential" section, as in figures 

 25, 27, 28, 30, and 31. 



Origin of the lamellae. — Since the prelamellar cavity attains 

 such a large size in comparison with the small size of the fruit body, 



1 For a full description and method oi interpretation of sections of the basidiocarp, 

 with the aid of diagrams, see Atkinson, Morphology and development of Agaricus 

 Rodmani. Proc. Am. Phil. Soc. 54: 309-343- P^- Q-^3- I9i5- 



