1911] ATKINSON—DICTYOPHORA AND ITHYPHALLUS 5 
primordium. The failure to find it in this connection in the speci- 
mens examined by me is not to be taken to mean that in some or 
in many specimens it is not so connected with the central primor- 
dium, but rather lends support to the view held by Burt that the 
medulla of the rhizomorph, when it does extend into the center of 
the young fruit body, is not concerned in the organization of the 
members of the mature plant, but that these are organized from the 
central primordium. 
The first evidence of the differentiation of the primordium is 
the gelatinization of the hyphae in the extreme upper portion 
just inside the cortical layer. This occurs in a small circular 
area which progresses centrifugally and downward from its edge, 
so that it becomes at first convex (fig. 17), and later campanulate, 
as it extends downward on all sides in the area, occupying the same 
relation to the central primordium and cortex. This forms the 
thick gelatinous middle layer of the volva. In the early stages 
of this gelatinous area, the swelling of the gelatinous substance, 
formed from the outer layers of the hyphae, crowds the hyphae 
apart and they form an irregular open network with large, more or 
less rounded gelatinous masses in the mesh. But with the forma- 
tion of more of the gelatinous substance and the broadening of 
this layer, many of the hyphae are stretched in a radial direction, 
extending from the tissue which later forms the inner layer of the 
peridium (figs. 19-22). 
While the development of this gelatinous layer is progressing, 
and soon after its inception, the fundaments of other parts begin 
to make their appearance. The fundament of the stem appears 
in longitudinal section (figs. 18, 19) as a delicate columnar struc- 
ture. The central portion of this structure consists of primordial 
or fundamental tissue, which is but little colored by the stain, 
while the fundament of its wall stains deeply and extends nearly 
up to the apex of the bell-shaped structure inside of the gelatinous 
layer. The bell-shaped area adjacent to the inner surface of the 
gelatinous layer, which takes a deep stain, is to form the inner 
wall of the peridium (D, figs. 19, 21). Lying directly next to this 
on the inner side is the fundament of the gleba (G, fig. 19), also 
a bell-shaped area, but not yet differentiated from the former. 
