INTRODUCTION 



IB 



The larger Fungi not described in this work are a few of the 

 Ascomycetes, including the Morel and its allies, the true ascus- 

 bearing Truffles and a limited number of Cup-fungi. 



The microscope is unnecessary for the determination of the 

 greater number of the Basidiomycetes ; nearly all are large and can 

 be satisfactorily examined by the unaided eye or with the assistance 

 of a hand-lens. A few forms found under Family iv Thelephoracece, 

 as Solenia and Cyphella, superficially resemble certain of the Ascomy- 

 cetes, as Peziza; but with a little experience even obscure forms 



may be easily determined with the aid of a 

 simple lens. In some genera of the Thelephoracece 

 a microscopic examination of the hymenium is 

 sometimes desirable. 



The Basidiomycetes are highly plastic and 

 variable. No one species is constant in all its 

 characters, and a single example seldom wholly 

 accords with any other single example of the 

 same species. Examples which appear to be 

 intermediate between allied, and sometimes 

 between not allied, species are frequently met 

 with. About one species in ten is perhaps fairly 

 well and distinctly marked, but all species will 

 at times present aberrant characters. Any one 

 character is liable to fail ; in the determination 

 of species, therefore, all the characters must be 

 studied together. 



The Basidiomycetes are so named on 

 account of the spores being borne on more or 

 less club-shaped cells named basidia (fig. 3). 

 They are commonly borne in fours, on slender usually short threads 

 or supports named sterigmata. In rare instances, however, the 

 basidium bears two spores or perhaps only one ; in these cases the 

 normal number of four is sometimes reverted to in well-developed 

 examples. In some species of the Tremellinacece the spores are 

 septate, and in some Gasteromycetes six or even more spores are 

 produced on a basidium. 



The spores are usually smooth and simple or composed of one 

 cell; they are sometimes echinulate or warted. The commonest 

 form is oval or round ; a few are multiangular. They are of micro- 

 scopic size, varying from about i8/t to 3/x. in length, and of various 

 colours. 



The character of the basidium with its four naked spores is one 

 of great importance, as it separates the Basidiomycetes from the 

 Ascomycetes. In the latter the spores are borne usually in a series 

 of eight, within microscopic transparent elongated colourless sacs 

 named asci (fig. 4) j the asci when ripe open at the apex and the 

 spores escape. 



In an examination of the spore-bearing surface or hymenium of 



Fig. 3. Pleurotus 



ostreatus Quel. 



A, basidium ; B, sterigma 



c, spore. X 750. 



