514 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
relatively small, and for comparison it was found desirable to study the 
general yield, weight, and size of the mushroom as grown in commercial 
mushroom houses in the vicinity of New York City. The mushroom 
clusters as they appear in the beds from the very youngest stages were 
plotted on quadrille paper, and each individual in a cluster was numbered 
and definitely located so that its whole history could be followed. The 
horizontal diameter of the apical region of the button was measured from 
day to day until it reached maturity, i.e., until it became fully expanded 
or failed to increase in size, turned brown, and died. In this manner the 
growth curve and fate of each plant were carefully studied. The percentage 
of buttons that developed normally, the relative rate of growth, and the 
size and weight of the plant were determined and recorded. The data 
thus obtained soon enabled me to predict after two days in the case of any 
particular button whether or not it would reach maturity. The results of 
these studies I shall report elsewhere; here I wish to report on the gill 
development as shown in the case of these buttons of known age and normal 
development. 
Fixations were made of white buttons that had just made their appear- 
ance on the surfaces of the beds, and of all later stages of normal buttons. 
Plants also that failed to show any increase in size and those that turned 
brown were fixed in a great variety of fixing solutions at different intervals. 
Agar-grown specimens of Coprinus ephemerus and C. stercorarius were fixed 
in a great number of different fixing solutions, the best of which was a 
dilute Flemming's weak solution. The plants were imbedded in paraffin 
and sections 5 to 25/x were made and stained. Sections of fixed buttons 
of Agaricus campestris were also compared with those of living material. 
Agaricus campestris 
The accepted facts as I have described them for Coprinus micaceus 
relative to the development of the simplest carpophore of the so-called 
endogenous types are: First, that the young, undifferentiated carpophore 
becomes divided into pileus and stipe rudiments. Second, the primordia 
of the hymenium arise as a circle or whorl of palisade pockets at or near 
the lower surface of the pilear rudiment, so that in a longitudinal median 
section of the young fruit body portions of this series appear as two densely 
staining narrow areas of hyphae on both sides of the button slightly above 
the center. Third, the growth of the hyphae of the pileus rudiment is 
marginal, that is, the youngest portion of the pileus is at its margin. I 
have pointed out for C. micaceus that there is no general annular gill cavity 
as maintained by Hoffmann, Atkinson, and others for a number of agarics, 
into which radially arranged plates of hyphae, primordia of the lamellae, 
grow, but that the palisade cells orient themselves on both sides of vertically 
arranged interlamellar spaces so as to form a series of gill cavities and gill 
