114 Journal of the Mitchell Society [June 



are usually eloujiated aud which discharge by the rupture of the 

 tip. There are usually eif>ht spores iu each sac, but this numlier 

 is in some cases iucreased by the division of the original ones 

 into several or many before they are discharged. Only a few 

 of the larger forms Avill be treated in this series of papers, and 

 the key to their families will be given later. 



Key to the Families of Basidiomycetes 



1. Hymenomycetes: Hymenium (spore bearing surface) exposed before ma- 

 turity and composed of gills, tubes or spines, or in some cases quite smooth. 

 (In those mushrooms which are enclosed in a cup when young the cup is 

 broken and the plant emerges before the spores are ripe.) 

 Basidia elongated and divided into four or 

 fewer cells by cross Avails ; texture of plant 

 toughly or softly gelatinous or waxy in the 

 sj^ecies here treated (of the very large 

 group of rusts Ave are treating only a few 

 species of Gymnosporangium, Avhich are gel- 

 atinous at one stage). 



Basidia arising from a specialized, thiek- 

 Avalled, constricted spore, Avhich is two- 

 celled in the species here treated (the 



other families of rusts are here omitted )..^e<:'ifZi'acfae (p. 115) 

 Basidia not arising as above, but from 

 hyphal threads, or in Saccoblastia from 



thin-Avalled, lateral, pendat sacs AuricuJariaceae (p. 119) 



Basidia divided across into several irregular 



cells; texture of plant fibrous and leathery ....Septohasidium (in Auri- 



culariaceae) (p. 125) 

 Basidia ovate, pyriform or spherical, divided 

 into two or four cells by longitudinal or 

 oblique walls 



Basidia arranged in roAvs of several; tex- 

 ture gelatinous Sirohdsidium (p. 128) 



Basidia single ; texture in one group gela- 

 tinuous and forming erumpent, folded or 

 convoluted masses; in another forming- 

 thin, resupinate, tough, leathery and co- 

 riaceous crusts ; in one gelatinous genus 



Avith the form and teeth of a 'iIy(hnim...TrcmeUaccae (p. 129) 

 Basidia long, slender, terete, forked above into 

 tAvo long branches, not diAdded into cells ; 



texture gelatinous or sub-cartilaginous Daciyinycetaceae (p. Ifa'O) 



Basidia not divided into cells and not forked, 

 mostly club-shaped 



Hymenium smooth; form of plant various, 

 but without sharp distinction betAveen 

 an expanded cap and a stem, sometimes 

 completely spread out (resupinate) on 

 the substratum. 



Texture tough, leathery and fibrous; 

 if branched, the branches not 

 rounded (except in a feAv sTpecies) ....Tlif le/ilioraceae 

 Texture softer, fleshy; plant cylin- 

 drical or club-shaped and un- 



