DEVELOPMENT OF EXOGENOUS SPECIES OF AGARICS 
45 
plant in radial section. The cut is made between the gills, but a 
portion of one gill joined to the stem appears in the photograph. 
The lightly stained area subadjacent to the palisade layer in figures 
77-80 represents the layer from which the hymenophore elements 
have branched. This extends not only into the gills but also between 
them in the pileus region, subadjacent to the hymenophore. The 
corresponding region is shown very clearly by Blizzard (9) in Omphalia 
chrysophylla (Plate VII, fig. 28) where certain hyphae give rise by 
digitate branching to the palisade layer. 
Entoloma 
Collection and Preparation of Material. — Embedded material of 
three species was turned over to me by Professor Atkinson, who had 
collected the young stages of E. flavijolium and E. grayanum from rich 
leaf mold in the Michigan Hollow Swamp near Danby, N. Y., in 
September, 1914. The material of E. cuspidatum was gathered during 
July, 1916, from humus among sphagnum in the woods near Seventh 
Lake, N. Y. All of the material was fixed in the field in medium chro- 
mo-ace tic acid. It was cleared in cedar oil and embedded in 52° par- 
affine. Sections were cut from 5 to 7 in diameter. Great difficulty 
was experienced in staining them. The young stages remained prac- 
tically unstained in a great variety of the common stains. Finally 
the method which proved satisfactory for some of the resistant 
Cortinarius (15) species, that of using tannic acid as a mordant followed 
by the fuchsin stain, was tried with fairly good results. Iron-alum 
haematoxylin was very satisfactory for older stages. 
E. FLAVIFOLIUM Pk. 
(Figs. 82-100) 
Early Stages. — The youngest button which was found is flask- 
shaped, about 3 mm. in length and i mm. through the widest part at 
the base (fig. 82). It is very compact in structure, especially in the 
region of the tip, where the hyphae are densely interlaced. The 
latter are slender and average about 2 .in diameter. The many 
prominent nuclei are an indication that active growth is taking place 
here. Already this has resulted in the differentiation of an enlarged 
apex, the pileus primordium, from that of the stem. As one passes 
