British Gastromycetes. 1 1 
at the base, corresponding to the point of attachment of the 
sporophore with the mycelium or vegetative portion of the 
plant. The thickened portion is known as the sterile basal 
stratum, and may form a spurious stem-like structure, as in 
Octaviania aster osperma, or project into the interior, in the 
form of an imperfect columella, as in most species of Hymeno- 
gaster . 
Sclerodermeae. The species belonging to the present order 
occupy an intermediate position between the Hymenogastreae 
and the Lycoperdeae, differing from the former in not being 
subterranean, and from the latter in the absence of a capil- 
litium and the indehiscent peridium. As in the Hymeno- 
gastreae, the peridium is thick, usually warted or rugulose 
externally, and but little differentiated, the trama springing 
from every part of its inner surface. Sorokin has shown 1 
that in Scleroderma verrucosum the hymenial elements of 
each cavity of the gleba originate from the branching of a 
single hypha, which enters the cavity at an early period of 
development. In Polysaccum the cavities of the gleba arc 
comparatively large and uniform in shape, being more or less 
polygonal in section. The walls of the trama are bright yellow 
in most species. In this genus the peridium appears to be 
completely formed at a considerable distance underground, as 
some species have a stout stem-like base from eight to ten 
inches long, and completely buried in the ground, the peridium 
alone appearing at the surface. From what is known in other 
instances, the stem probably remains rudimentary until the 
spores are mature, when it elongates for the purpose of raising 
the peridium to the surface, thereby facilitating the dispersion 
of the spores. 
Nidularieae. The first indication of differentiation pre- 
sented by the young sporophore consists in the gelification 
of a zone of the homogeneous weft of hyphae which com- 
mences near the base and extends upwards, parallel to, and 
at some distance within, the periphery, the external portion 
Sorokin, Ann. Sci. Nat,, Ser. 6, vol. iii. p. 30. 
