316 DIVISION II.—COURSE OF DEVELOPMENT OF FUNGI. 
falls away (Vittadini). In some, perhaps in most species, as for instance in Bovista 
plumbea and Lycoperdon perlatum, according to Tulasne and Vittadini, the dis- 
organisation affects the whole of the outer peridium and it becomes changed into 
a slimy mass, which turns as it dries into a brittle and almost structureless mem- 
brane. 
. The structure of the peridium is more complicated in Geaster. G. hygrometricus is 
up to the period of perfect maturity a roundish body, which may be of the size of 
a hazel-nut and remains beneath the surface of the ground (Fig. 146). Six layers 
may be distinguished in the peridium in a vertical longitudinal section a short time 
before the compound sporophore is mature. The outermost layer is of a brownish 
colour, flaky and fibrous, and is continued on one side into the mycelial strands which 
spread through the soil and on the other passes into the second layer; a thick stout 
brown membrane entirely covering the compound sporophore. This is followed 
towards the inside by'a white layer, which is more largely developed at the base of the 
compound sporophore than elsewhere and is immediately continuous at that spot with 
the inner peridium and the gleba. Both of these last-mentioned layers are formed of 
stout closely-woven hyphae running in the direction of the surface, and may be combined 
under the name of the 2rzllose layer. The inner of the two is lined on the inside by the 
collenchyma-layer (Fig. 146 c), except where its basal portion passes into the gleba. 
This layer is cartilaginously gelatinous and consists of hyphal branches of uniform 
height connected together without interstices, 
which are placed palisade-like vertically to the 
surface and are bent as they spring from the 
hyphae of the fibrillose layer. The strongly 
thickened stratified walls of the cells of this layer 
have great capacity for swelling. Inwards from 
the collenchyma is a white layer, the innermost 
region of which is the inner Zeridium, while 
the outer, which inay be called the sfl/t-layer, 
consists of soft loosely woven hyphae which 
pass at many points into the inner peridium. 
When the Fungus is quite matured, the outer 


oe N \ 
RN 1 2 
EN]. 

Fic. 146. Geaster hygrometricus. Vertical median 
longitudinal section of a fully grown nearly mature 
;pecii very slightly ified. c collench layer, 
£ gleba, the apex of which is beginning to assume a dark 
colour as the spores ripen. 


peridium, through the influence of moisture and 
through 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 hecomes convex. The 
split-layer is by this means so torn to pieces that its constituent parts remain hanging 
as perishable flakes, some to the collenchyma, 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 fimbriatus 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. The fibrillose layer is comparatively thinner in these and other 
species than in G. hygrometricus and is not divided into two layers. The collenchyma- 
layer consists of large-celled transparent pseudo-parenchyma, which swells up strongly 
in water and causes the opening of the peridium and the convexity by its expansion, 
whether this is due to swelling only, or perhaps to growth also. In G. fornicatus, 
