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 fibrillose layer. The inner of the two is lined on the inside by the 

 collenchy ma-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 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 

 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 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 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. fomicatus 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, 



FlG. 146. Geavtrr hygrometricus. Vertical median 

 longitudinal section of a fully grown nearly mature 

 specimen, very slightly magnified, c collenchyma-layer, 

 g gleba, the apex of which is beginning to assume a dark 

 colour as the spores ripen. 



