20 GENERAL CONSIDERATIONS 



gelatinous or non-gelatinous hyphal extensions. In general pilocystidia 

 as such are very rare or absent in the genus Hygrophorus, and when 

 present are more like a terminal hyphal cell. We have not found them 

 to be of any significance taxonomically. In species which have the 

 epicutis of the pileus in the form of a dry trichodermium the end cell 

 of the epicuticular hyphal element may be cystidioid in shape; i.e., 

 broadly clavate to somewhat fusoid-ventricose, but this kind of struc- 

 ture is tied up more with the development of the hymeniform type of 

 pileus epicutis than with scattered true pilocystidia. Caulocystidia are 

 also of a relatively undifferentiated type, mostly more or less resem- 

 bling hyphal tips. Their chief claim to interest is that undoubtedly, in 

 the fresh state, they will show some valuable color reactions with cer- 

 tain chemicals. 



We regard it as curious that this genus shows so little in the way of 

 cystidia when such genera as Mycena are noted for the presence of 

 diverse cystidial types. Whether this argues for or against the connec- 

 tion we have regarded as existing between the two genera depends on 

 one's interpretation of the situation. We assume that the cystidia as 

 found in Hygrophorus represent a primitive condition, and it seems 

 logical further to suppose that the diverse types of cystidia found in 

 Mycena are derived from that primitive condition. But, it should also 

 be remembered that cystidia are a feature of nearly all Hymenomy- 

 cetes, and that these structures must have originated from basidia inde- 

 pendently on numerous occasions. 



Gill Trama (Figs. 3-6) 



The arrangement of the hyphae forming the gill trama has for years 

 been the basis on which Hygrophorus has been subdivided into three 

 genera or three subgenera or sections, depending on the author. We 

 have used it to delimit the sections of subgenus Hygrophorus. 



1. In section Hygrophorus (Fig. 3) the hyphal arrangement is 

 termed divergent or bilateral because the hyphae extend downward 

 and outward from a thin central strand of somewhat interwoven to 

 nearly parallel hyphae. The hyphae vary in diameter with the species 

 but usually are 4-8 fi broad. They are thin- walled and mostly colorless. 

 In age some of the component cells may inflate somewhat, but they 

 do not become sphaerocyst-like. This hyphal arrangement is easily 

 demonstrated by freehand sections cut from fresh material, but in re- 

 vived material one sometimes encounters certain difficulties. Appar- 

 ently in the process of drying, the hyphae in the area of divergence 

 straighten out, and when sections are made from this dried material 

 and revived in KOH, the hyphae do not assume their original arrange- 



