membrane, volva, which is ruptured by the gro-^vth of the plant ; the 

 upper portion remaining on the pileus forming patches, warts or 

 scales, the lower portion loosely surrounding the base of the stem. 

 In many species the Tolva is imperceptible. 



The gills are variable in size and shape ; when all are of equal 

 length they are simple, when shorter ones are interposed they are 

 unequal. Each gill has commonly a central portion, trama. The 

 surface on both sides of the gills is formed by the spore-bearing 

 membrane, hymenium. The ordinary floccose trama is sometimes 

 replaced by a layer of globular cells intermixed with vessels con- 

 taining a milky fluid. 



The hymenium is made up of parallel cells, the extremities of 

 which form the surface. They are of three kinds ; barren thread- 

 like cells, parajjhjses ; other cells, lasidia, which are somewhat 

 larger and are attenuated towards the outer extremity which 

 is sometimes slightly knobbed and bears from one to six, ordi- 

 narily four, minute points, sterigmata. Each sterigma supports 

 a seed or spore. Sometimes may be found a third kind of cells, 

 antheridia, simple, very delicate and Mled with fluid containing 

 minute particles which have a rajiid swarming motion. These cells 

 disappear before the basidia are developed. 



The spores are variously shaped, globular, ellijitical, straight 

 or cuiTed, obliquely truncate at one extremity, legumeniform, 

 generally smooth but sometimes rough or echinulate. From the 

 spore under circumstances favourable for germination is produced a 

 a simple or branched filament which alone is incapable of fructifi- 

 cation, but when the filaments of many spores unite, or when the 

 filament of a single spore has become sufficiently compound, a soft 

 white web, mycelium, is formed, from which springs the reproduc- 

 tive organ ordinarily regarded as the whole of the plant. 



The measurements of spores in the accompanjang list have in 

 each instance been made with the assistance of a stage micrometer. 

 If the spores in any particular species vary in size those of the 

 largest kind have been taken as the standard. The longest dia- 

 meter only has been given. The term elliptic I have used to denote 

 an oval in which the longitudinal and transverse diameters are in 

 58 



