Nov., 1922] LEVINE LAMELLAE IN AGARICUS CAMPESTRIS 515 
Anlagen. Where the ends of the paHsade hyphae meet, the interlamellar 
space, the gill cavity Anlage, is at first tightly closed and does not appear 
as an open interhyphal space even with high magnification. The hyphae 
between two such adjacently formed palisade layers constitute the Anlage 
of the trama. These hyphae can be traced back into the rudiment of the 
pileus and into that of the stipe. 
The results I obtained in Agaricus campestris are similar to those ob- 
tained with Coprinus micaceiis. Atkinson and his students have noted 
that the fixation of larger types of gill fungi is exceedingly difficult. The 
large continuous annular gill cavity which they describe is, as I find, an 
artefact due to poor fixation. I have studied the development of Agaricus 
campestris from material grown under observation in mushroom beds and 
have been able to follow the development, growth rate, etc., of these plants 
from the time they appeared on the surface of the bed to the time they are 
fully expanded. I have compared sections of fresh and fixed material at 
all stages. It is at once discovered in such studies that not all the buttons 
which appear in young clusters are destined to reach maturity, as noted by 
Duggar (1915) and others. Studies of growth rate, etc., enabled me to 
predict which buttons are going to develop and which are not. Generally, 
after 72 to 96 hours after the appearance of the buttons on the substratum 
those that are destined to develop can be distinguished from those that 
are not. At this time there is no conspicuous difference in their appearance, 
but only in their ability to grow as shown by their previous rate of growth. 
Later on, those that do not develop turn brown.. 
Young plants that showed constant increases in size by actual measure- 
ments were sectioned free-hand and studied quickly thereafter under the 
microscope. The sections showed, in the young and late stages of the 
development of the palisade pockets and gill primordia, no annular gill 
cavity. The hymenophore primordia and the rudimentary gills shown in 
Plate XXVIII, figures 1-16, are firmly attached to the fundamental tissue 
of the stipe below, just as they are in Coprinus micaceus, C. ephenierus, and 
C. stercorarius mentioned below. On the other hand, specimens similar as 
to age and size fixed in the various commonly used fixing solutions showed 
within twenty minutes after fixation two large holes placed right and left 
of the stipe (figs. 35-51), just below the young pileus and corresponding 
exactly to the annular gill cavity described by Atkinson. It should be 
added that great care must be taken in making these sections since the 
forming palisade pockets weaken in the tissue connection between pileus 
and stipe. Young buttons that showed no sign of developing normally 
and those that turned brown were also studied in free-hand sections. These 
showed conditions similar to that in the unfixed living plants. There was 
no annular gill cavity, and the gill Anlagen were in connection with the 
fundamental tissue below the pilear region (figs. 17-22). When the ap- 
parently dead carpophores were fixed in chrom-acetic and various other 
