246 BOTANICAL GAZETTE [OCTOBER 
becomes the stem. The tissue on the outside of it corresponds to 
the edge of the pileus, but its hyphae continue without interruption 
or change into the outer surface of the stem below. 
In 1874 R. Hartic,'5 in his study of the development of Agaricus 
melleus, says that “the investigation of the earliest condition of the 
fruit body of Agaricus melleus shows that here, as well as in the 
Agaricaceae not provided with a veil, the pileus arises through a 
superficial annular furrow which in the beginning is completely open 
to the outside, and that later through growth of the marginal hyphae 
of the pileus and of the stem the annular furrow becomes covered 
over with a hyphal layer, the veil.” He further says that if one 
compares his fig. 20 (which shows the veil covering the hymenial 
tract) with DeBary’s fig. 26 (1. c.) of the young Agaricus campestris, 
“it appears from the agreement of the two figures that the con- 
jecture is justified that also by this last fruit body in the region of the 
hymenial tract a subsequent growing together of the hyphae of the 
pileus and stem has taken place.’’ Longitudinal sections of the 
young fruit body of A garicus campestris at this stage do give the sug: 
gestion that the veil originates as Hartic described for Agaricus 
melleus. DEBary evidently did not study the very young stages of 
Agaricus campestris, for all his figures of longitudinal sections show 
the veil covering the hymenial area. It seems that without reinves- 
tigating the question he adopted Harric’s suggestion that the 
development in Agaricus campestris followed the same course as that 
described by Harrie for Agaricus melleus, In his later work?* he 
says in reference to those forms with a “marginal veil” (velum 
partiale of Fries): “Up to the first formation of the pileus 0? the 
summit of the stipe-primordium the phenomena are the same a 
essential points as in the gymnocarpous forms” (referring 2 his 
figures of Collybia dryophila, p. 55). “The young pileus is entirely 
delimited from the stipe by a transverse annular furrow runmns 
along its future hymenial surface, But then the superficial hyP 
layers of the stipe and of the young pileus send out numerous branches 
toward one another from the edges of the furrow; these unite into 
15 Wichtige Krankheiten der Waldbaume, etc. 25. pl. 106. 1874- 
*6.Comparative morphology and biology of the fungi, etc. 289-29° 
English edition. 
1887- 
