THE RECEPTACLE 



37 



exoperidium may be tough and leathery, and in Geaster it splits 

 downwards from the apex into several triangular lobes. In 

 Bovista it is fragile and evanescent. In Lycoperdon it breaks 

 up into granules, warts, or spines, which adhere for some time 

 to the inner and persistent peridium. In Polysaccum and 

 Scleroderma the periderm is not differentiated into two coats, 

 but in the latter the exterior cracks into warts or frustules. 

 In this form the receptacle is an entirely closed envelope, in 

 which the fructification is completely concealed until it is 

 quite mature, and then it either opens with a small orifice or 

 is irregularly ruptured. Hence the light is not essential to 

 the perfection of the fruit, and the' peridium might almost as 

 well remain in the soil, which it has a tendency to do in some 

 species of Scleroderma, and does completely in the Hypogaei. 

 In the majority of species the substance of the peridium is 

 tough and leathery, and so persistent that it often remains 

 behind long after dehiscence and the dispersal of the spores, e 

 A third form of receptacle is the excipulum or cup-shaped 

 receptacle, which, although often closed when young, is soon 

 expanded so as to expose the disc or 

 hymenium to the full light; in fact 

 they are heliotropic, for they turn the 

 disc as much as possible towards the 

 sun. The type of this form is to be 

 found in the old genus Peziza, now split 

 up into many genera, but the form and 

 structure of the excipulum is the same 

 throughout (Fig. 19). The external 

 stratum of cells does not form a 

 separate cuticle, but is continuous with 

 the subjacent cells, and usually consists Fk-19-— Keoeptaole of Pezim, 



„ ,. , , . ., ... with section and ascus. 



of smaller or elongated cells, which 



may be coloured, and either mixed with or prolonged into 

 hairs, usually most strongly developed about the margin of the 

 excipulum. Within the cuticular layer lie the subhymenial 

 cells, on which rests the hymenium or fruit-bearing surface. 

 The attributes of this form, therefore, are a cup -shaped 

 receptacle, with the mouth turned to the light, and composed 

 of an external and internal series of cells, the latter supporting 



