CHAPTKll I 



THE HYMENIUM— BASIDIA AND PAEAPHYSES— NUCLEAR PHENO- 

 MENA—THE COLOUR OF SPORES— TWO-SPORED BASIDIA IN 

 CULTIVATED VARIETIES OF I'SALLIOTA CAMI'J'JSTL'IS—OCCA- 

 SIOXAL STERILITY OF COPRINUS FRUIT-BODIES— CYSTIDIA— 

 FUNGUS GNATS, SPRINGTAILS, AND MITES— POSITION OF THE 

 HYMENIUM— COMPARISON OF THE BASIDIUM WITH THE ASCUS 

 —THE EFFECT OF SUNLIGHT UPON SPORES 



The hynieniuin of most Hymenomycctes is made up of spore- 

 bearing basidia and of sterile paraphyses. In a great many 

 species, it consists solely of these two kinds of elements; but in 

 a number of others, cystidia and other specialised cells enter into 

 its structure. 



Basidia and Paraphyses. — It is a general rule, Avith compara- 

 tively few exceptions, that each basidium produces four sterigmata. 

 Each sterigma tapers conically, and bears at its apex a single spore 

 which, although sometimes spherical, in most cases is oval in shape 

 (Fig. 55, p. 162). The spore-wall in some species bears spines, but 

 usually is quite smooth. A sterigma, at the point of attachment to 

 its spore, has an extremely small diameter Avhich in many instances 

 measures only 0-5 fi (Plate I., Fig. 34; Plate III., Fig. IG). This 

 narrow neck is of great importance, for, when a spore is set free, 

 the neck breaks across and the spore is projected Avith considerable 

 violence straight outAvards from the basidium.^ It must be at 

 the neck that the propelling force comes to be exerted. 



The spores of all Hymenomycetes are very adhesive, and on con- 

 tact readily adhere to one another or to any object upon which they 

 settle. As if to prevent them touching one another during develop- 

 ment and discharge, the four spores on a basidium are borne 

 laterally on the sterigmata in such a manner that they are situated 

 as far apart as possible (Plate I., Fig. 3, (' : Plate 111., Fig. IG). 



* T'idc infra, Cliaj). XI. 



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