6 
GEORGE F. ATKINSON 
portion of the carpophore stains more deeply. The hyphae of the 
peripheral portion have somewhat thicker walls and less protoplasmic 
content than those of the interior, i. e., of the pileus and stem funda- 
ments. The walls of these hyphae are well stained with the haema- 
toxylin, and this portion contrasts rather clearly with the interior 
because it is more deeply stained and also because the meshes of the 
tissue are somewhat larger. The features which mark the differentia- 
tion of the internal portion into pileus and stem are the very slight 
indication of the annular gill cavity, the appearance of a constriction 
between the stem and pileus fundaments, and the abrupt narrowing 
of the internal portion, so that the pileus primordium appears as a 
small round projection from the broader basal portion, the primordium 
of the stem. The looser, more deeply staining tissue surrounding the 
• pileus and stem primordium is fundamental tissue, the outer portion of 
which may be regarded as the "universal veil," though its inner limits 
cannot be clearly defined. 
On the exterior the young carpophore does not yet show any con- 
striction because the enveloping zone of fundamental tissue has not 
yet become subject to distortion from the internal changes of form. 
This condition exists until some time after the origin of the primordium 
of the hymenophore, when the expansion of the pileus becomes greater 
than the lateral expansion of the stem, and an external constriction 
is then evident. 
The hyphae of the interior portion of the very young fruit body are 
3-4.5/^ in diameter, have very thin walls, and the rather scant cyto- 
plasm alone appears to be stained. 
Character of the pileus primordium. — The annular gill cavity is 
formed by the more rapid growth and extension of the surrounding 
tissue. It appears between the margin of the pileus and the stem 
fundaments. The absence of a more deeply staining central portion 
in the upper part of the young fruit body contrasts strongly with the 
condition in Hypholoma described by Miss Allen ,4 in Lepiota clypeo- 
laria,^ and with the condition described by Fayod^ as the rule for the 
Agaricaceae. Jt agrees with the condition found by myself in Agaricus 
^ Allen, Caroline L. The development of some species of Hypholoma. Ann. 
Myc. 4: 387-394- pls- 5-7- 1906. 
^ Lepiota clypeolaria will be described in another paper. 
^ Prodrome d'une histoire naturelle des Agaricines. Ann. Sci. Nat. Bot. VII, 
9:181-411.^/5.(5,7. 1889. 
