ridges. If no palisade c e differ 
218 BOTANICAL GAZETTE [SEPTEMBER 
been stated, the hyphae in the palisade layer are not crowded 
enough to produce any great pressure, and it would seem that the 
origin of the gill salients, which appear as downward folds of the 
palisade, is due entirely to the growth and elongation of radial lines 
of hyphae in the hymenophore, which push the palisade down in 
folds, the young gills, as described for Hypholoma sublateritium (1) 
and Siropharia ambigua (25). The gill salients are broader than 
in P. squarrosa, and this may be due to the fact that when thrown 
into folds by downward growth of the hyphae above, because of the 
less crowded condition of the palisade, they are not subjected to as 
great lateral pressure as in that species. 
Fig. 39 is from a tangential longitudinal section of a basidiocarp 
with sterile gills, that is, the palisade layer has failed to form. The 
_cystidia, which develop from the trama of the gill, are very notice- 
able as deeply staining clavate bodies. The situation presented 
here is interesting because of its bearing on the question recently 
raised by LevINE (21) in regard to the origin of the lamellae in the 
Agaricaceae. The points of growth for the origin of the lamellae, as 
described by ArkmNson in several species of the Agaricaceae, 
including Agaricus rodmani (8) and Coprinus comatus, C. atramen- 
tarius, and C. micaceus (9), occur in radial areas of hyphae in 
the hymenophore, which develop centrifugally and grow down 
more rapidly than the other hyphae. These areas are the gill 
tramae, and push the palisade into regularly spaced folds, which 
are the salients of the lamellae themselves. This method 
here. 
of origin of the lamellae occurs in the three species described 
According to Levine’: S$ conception, radiating ridges of palisade = 
cells arise in the fundamental tissue, and by continued differentia- ee 
tion and downward growth of new palisade cells, split apart. Bee 
adjacent halves of en come together and unite 
to form a lamella. The trama of the gill would ee be formed by _ 
the coming together of preexisting palisade cells ae! ; 
ee 
ee eal) be formed. In this case, however, no 
