22 GENERAL CONSIDERATIONS 



3. In Hygrotrama the hyphal arrangement is more interwoven 

 than parallel, but the species in other respects appear to be most closely 

 related to those of section Hygrocybe on the characters of stature and 

 epicutis of the pileus. 



4. In section Hygrocybe (Fig. 5) the gill trama is composed of 

 hvphae which are parallel to somewhat interwoven. In this type the 

 width of the hvphae may be great (20 /x or more at times), and the 

 individual cells are usually elongated. One of the most extreme exam- 

 ples of this type is found in H. conicus (Fig. 5). In others, as in H. 

 coccineus, the tramal hyphae are more narrow and shorter (Fig. 6). 



In summary, we have found from our studies that the arrangement 

 of the hyphae in the trama of the hymenophore in Hygrophorus is a 

 generally reliable character by which to distinguish sections of the 

 subgenus Hygrophorus, but we are not convinced that the differences 

 are of sufficient magnitude to justify recognizing the various sections as 

 genera. We now believe that from a careful study of hyphal arrange- 

 ment in the hymenophore on a large number of species in the fresh 

 condition, it will be shown how one of these types originated from the 

 other. It will then be possible truly to evaluate the meaning of the 

 different arrangements in terms of a classification of the species and 

 their phylogeny. In view of the difficulties with revived material, and 

 the almost uniform poor condition of much of the older authentic mate- 

 rials as dried, we feel that a study made from such materials is too 

 likely to prove misleading to justify the work being done in that 

 manner. 



Pileus: Context and Cutis 



The hyphae of the context are disposed generally in a direction 

 radial to the stipe, but in relation to each other they may be loosely to 

 compactly interwoven to subparallel or parallel. Usually only one 

 hyphal system is evident, but in some species a distinct laticiferous 

 system is also to be noted. The cells of the structural hyphae for the 

 most part inflate as maturity is approached or passed in the enlarge- 

 ment of the pileus. In a few species peculiar brown granules are noted 

 in the hyphae on mounts made in Melzer's reagent, but for the most 

 part the microscopic structure of the context offers little of value to the 

 taxonomist. 



The surface layers (the cutis), however, offer many features of 

 great taxonomic value and will be discussed in the approximate order 

 of their complexity. 



Type 1. The simple cutis (Fig. 7, a,b): In species with a dry 

 glabrous pileus a section through the latter reveals no differentiation 



