510 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
appears. The formation of the gills resembles that of the other angio- 
carpous forms he described earlier. 
De Bary's (1866) work followed soon after Hoffmann's. He described 
three species^ of agarics in which he claims to have observed that the young 
carpophore begins as a mass of delicate and densely interwoven hyphae. 
Soon this small ball of hyphae becomes divided into two parts by the 
development of a horizontal annular gill cavity which in median longitudinal 
section appears as two openings in the upper and inner portion of the 
undifferentiated hyphal mass. The region lying above a horizontal plane 
through the gill cavity forms the pileus, while the part below forms the 
stipe. The layer of hyphae directly above the gill chamber grows into it 
and forms the lamellae. De Bary's figures of Coprinus micaceus in young 
stages clearly shows the edges of the gills in contact with the stipe, though 
he does not emphasize their connection with it. 
R. Hartig (1874) claims that in Agaricus (Armillaria) melleus the lower 
surface of the pileus forms an exposed hymenium. A vigorous downward 
growth of the hyphae sets in from the upper surface and margin of the pileus 
and a corresponding upward growth of the superficial hyphae of the stipe, 
thus forming a weft of hyphae or a veil hiding from view the hymenium. 
Brefeld (1877) claimed that the carpophore Anlage is a hyphal cell that 
gives rise to a number of branches which intertwine, forming a small mass 
of coiled hyphae. This mass increases in size, and internal differentiation 
ensues. The whole carpophore is covered by a loose layer of globular cells 
which Brefeld held is morphologically equivalent to the volva of the Ama- 
nitas and differs only in that in the latter genus the structure is more compact. 
Brefeld held that the lamellae arise as compact bundles of parallel hyphae 
each of which has apical growth. Numerous branches are produced which 
turn to the right and left to form the hymenium. The growth of the 
lamellae results finally in the adhesion of their edges to the surface of 
the stipe. 
Fayod (1889) contributed his results of the study of a long series of 
agarics in which he denies Hoffmann's conception of the method of develop- 
ment of the pileus and hymenium. This author maintains that in the 
upper portion of the spherical button a layer of dense hyphae is differentiated 
which has the form of an inverted bowl that he calls the couche pileogene. 
A great number of workers who have studied the sexuality of the Basidi- 
omycetes since the nineteenth century have reported incidentally various 
phases of the development of these plants, but have not contributed any- 
thing of importance to the question of the origin of the gills (see Levine, 
1913)- 
From the time of Fayod nothing was done until the appearance of 
Atkinson's (1906) work. This took up the question and the manner of 
origin and development of the carpophore of Agaricus campestris vars. 
3 Agaricus campestris, A. praecox, and Coprinus micaceus. 
