Nov., 1922] LEVINE — LAMELLAE IN AGARICUS CAMPESTRIS 519 
below the margins of the young gills. Figure 57 represents a view near 
the stipe region, and we see the gills already torn away from the tissue 
below. This fundamental tissue below the gills has collapsed partly and 
has formed a thin, regular curve (in outline), deeply stained, which marks 
the upper surface of the annulus (A). The fine radial grooves which are 
noticed on the rings of annulate species and on the upper portions of the 
stipes of exannulate species are marks of this continuity which exists be- 
tween the hyphae of the stipe and the tramal elements of the gills. Harper's 
(1913, 1914) excellent photographs of annulate and exannulate fungi bring 
out these facts clearly. The gills and the furrows seen in outline are ap- 
proximately equal in number, and the shape of the margin of the gill seems 
to indicate that it is the counterpart of the furrow of the annulus. 
It appears, then, from the study of both the living and the dead buttons 
of Agaricus campestris that the method of the development of the lamellae 
is essentially the same as in Coprinus species. The early stages in the 
formation of the gills in Agaricus show more clearly the relation of the 
tramal elements to the palisade cells and that they form bridges of hyphae 
between the pileus and stipe regions. The orientation of the palisade cells 
on both sides of the trama forms typical arches enclosing gill cavities. One 
apparent difference between the early gill formation in Coprinus and in 
Agaricus species is that in the latter the palisade cells which arise from the 
lower portion of the trama are at first shorter than those that arise higher 
up from the pilear region, thus giving the young gill a wedge shape in 
section, the gill cavity forming from the beginning a true arch. It becomes 
clear that, as seen in section, the arch of palisade cells is the unit of structure 
of the hymenial surface. This palisade tissue originates as a mere pocket 
which elongates radially with the marginal growth of the pileus. These 
palisade groups widen on both margins by the formation of new elements 
which bud out from the trama. These new elements face each other, and 
the interpalisade space is the forming gill cavity. 
Among the normal plants of Agaricus campestris grown from pure 
spawn there often appeared a button which was at first indistinguishable 
from the other buttons, but which became characterized by the smallness 
of the pilear region. These plants never mature as far as I have observed. 
Sections of these buttons were made, and it was found that the basal portion 
of the plant consisted of an undifferentiated mass of hyphae the elements of 
which are very narrow and very much intertwined, taking in general a 
uniform stain. The apical portion, which was marked off by a superficial 
annular furrow, was found to consist of five zones of tissue (figs. 62-65, 
PI. XXXI). The central part consists of a hemispherical mass of inter- 
twining hyphae, recalling at once Fayod's couche piUoglne. This structure 
stained heavily. The hyphae in the middle of the central region are very 
much entangled, as mentioned above. Toward the surface, the hyphae 
become radiate and blended with a zone of much more faintly staining 
