British Gastromycetes . 17 
the inner peridium, while the outer, which may be called the 
split-layer, consists of soft, loosely- woven hyphae, which pass 
at many points into the inner peridium. When the fungus is 
quite matured, the outer peridium, through the influence of 
moisture and the swelling of the collenchyma-layer, bursts 
outwards from the apex in a stellate manner, forming several 
lobes which turn back, so that the upper surface which is 
covered by the collenchyma becomes convex. The split- 
layer is by this means so torn to pieces that its constituent 
parts remain hanging as perishable flakes, some to the col- 
lenchyma, some to the inner peridium. It is known that the 
collenchyma-layer retains its hygroscopic qualities a long time, 
and the outer peridium remains a long time lying on the soil, 
stellate in shape, spreading out its rays in moist weather and 
bending them inwards in dry. The flaky investment of the 
outer peridium is often more strongly developed in Geaster 
fimbricatus and G. fornicatus than in G. hygrometricus ; and in 
G. fornicatus it is composed of the finest of hyphae ; it tears 
away from the fibrillose layer when the peridium is ruptured 
and lies on the ground beneath the peridium as an open 
empty sac. The extremities of the lobes remain for the time 
firmly united to the margin of this sac, and as the collenchyma- 
layer expands greatly, the star formed by it and the fibrillose 
layer, especially in G. fornicatus , becomes convex upwards, 
and carries the inner peridium on the apex of the convexity * 
(Fig. 42). In many species of Geaster there is a distinct 
columella, often club-shaped and extending to half the height 
of the inner peridium. From this columella the threads of 
the dense capillitium radiate to all points of the inner peridium 
to which they are attached (Fig. 27). 
It is more than probable that the species included in the 
exotic genus Cycloderma described by Klotzsch 1 are merely 
species of Geaster that have been collected before the ex- 
pansion of the peridium. The two are identical in structure. 
Nothing is known respecting the earliest stage of development 
1 Linnaea, VII. p. 203. 
C 
