lO 



BOTANICAL GAZETTE 



[JULY 



trama of Pluteus seticeps Atk. MSS (see footnote i), made from 

 a freehand section which shows the typical structure of the trama 

 of mature plants having this type of trama. The details of this 

 cam be seen more clearly in text fig. 8, which is a reconstruction 



from two photographs taken at slightly 

 different foci. 



The cells composing the original 

 trama in this species, and many other 

 species examined, enlarge to the same 

 size as those of the converging filaments 

 arising in the subhjTnenium. This may 

 not be true, however, of all species of 

 Pluteus. In some specimens of Pluteus 

 longistriatus the cells of the original 

 trama seem to have entirely escaped the 

 general expansion and remain slender, 

 even in the mature pileus. 



These downward growing filaments, 

 originating as they do in the subhyme- 

 nium, the same region from which the 

 cystidia originate, and having the same 

 general characteristics as cystidia (en- 

 larged cells with scanty protoplasmic 

 content), seem to represent a type of 

 internal cystidium development. In 

 some species of Pluteus a necklike constriction'occurs near the apex 

 of the external cystidium, and also on these internal outgrowths. 

 These internal cystidia are at first binucleate, the 2 nuclei occupy- 

 ing a central position, as in the other cystidia, but the nuclei 

 degenerate before the cystidia have attained the length shown in 

 text fig. 6. 



Tubaria furfuracea 



Fig. 8. — Culmination of 

 downward outgrowths from 

 subhymenium as seen in 

 Pluteus seticeps; outlines ob- 

 tained from combination of 2 

 photomicrographs made at 

 slightly different focus on free- 

 hand section. 



EARLY DIFFERENTIATION OF PRIMORDIUM OF BASIDIOCARP 



A median longitudinal section of an undifferentiated primordium . 

 of a basidiocarp is shown in figs. 51 and 78, the latter being a higher 

 magnification of the upper portion of the former. It consists of 



