342 ATKINSON— MORPHOLOGY AND [April 23, 



hymenophore is still entirely in the primordial stage (see Fig. 11) and ex- 

 tends for a considerable distance down on the surface of the upper part of the 

 stem fundament. 



Fig. 8. (No. ^%.) Longitudinal section of the same basidiocarp, 

 "tangential" to the hymenophore and annular cavity (see Fig. 16). 



PLATE X. 



Fig. 9. (No. "%.) More highly magnified view of the transection of 

 the hymenophore primordium shown in Fig. 3 ; stem axis at the left. In 

 the darker area (hymenophore primordium) the hyphae extend downward 

 and obliquely outward toward, and some projecting into, the veil fundament 

 below, which consists of a loose mesh of interwoven hyphae. 



Fig. id. (No. -%•) More highly magnified view of the transection 

 of the hymenophore primordium and annular cavity shown in Fig. 5 (axis of 

 stem at the left). 



Fig. II. (No. 1%.) More highly magnified view of the transection of 

 the hymenophore primordium and annular cavity shown in Fig. 7 (stem axis 

 at right). The hymenophore primordium extends down over the upper part 

 of the stem outer surface. Veil fundament in the angle below, the ground 

 tissue tearing apart and separting from the fimbriate under surface of the 

 hymenophore 



Fig. 12. (No. %.) Transection of hymenophore and annular cavity, 

 showing same view as Fig. 11 (stem axis at right) but in another basidio- 

 carp and slightly older stage; the portion of the hymenophore primordium 

 on the upper part of the stem fundament has become transformed into the 

 level palisade stage. 



Figs. 13 and 14. (No. %■) Section of another basidiocarp showing 

 the hymenophore and annular cavity in same stage as in Fig. 10, at different 

 magnifications (stem axis at right). Hymenophore primordium with fim- 

 briate edge. Ground tissue below (veil fundament) breaking away from the 

 fimbriate surface of the hymenophore as a result of the tension produced by 

 the rapid increase in number and size of the elements of the hymenophore and 

 the lagging behind of the ground tissue below, thus forming the annular 

 cavity. These sections are radial and parallel with the direction of the later 

 lamellae. The elements of the hymenophore here are somewhat clustered, the 

 slender ends of the hyphse clinging in groups as the lower surface of the 

 hymenophore is loosened by the tension of the increase above. 



Fig. 15. (No. -%•) "Tangential" section of the hymenophore 

 primordium, more highly magnified view of the hymenophore and general, 

 annular, prelamellar cavity shown in Fig. 6. Note the fimbriate lower sur- 

 face of the hymenophore primordium, and the loose ground tissue (primor- 

 dium of veil) below separating from it and forming the annular cavity. 

 The structure of the hymenophore primordium is homogeneous, there is not 

 the slightest evidence of gill salients, or of ridges of any sort, which pre- 

 cede or have any relation to the lamellae which are to arise later. 



Fig. 16. (No. 12/;.) "Tangential" section of hymenophore primor- 

 dium, annular cavity and veil fundament, a more highly magnified view of 

 this part of the basidiocarp shown in Fig. 8. Details as in Fig. 15. 



