8 GENERAL CONSIDERATIONS 



released enzymes are very important characters, as for instance the 

 change to black in H. conicus and its variants, H. singeri, and to some 

 extent H. tahquamenonensis. In the Rubentes of section Hygrophorus 

 these reactions may be slow to develop but show up as spots on the 

 gills by the time the fruiting body is mature; or from gills which are 

 white at first there may be a progression to dark vinaceous red in age. 

 Other species may show a color change to green on some part in age 

 or on bruising. 



A chemical study of the pigments in Hygrophorus would be inter- 

 esting, but we have not ventured in this direction. The problem is dif- 

 ficult because there are so many components in many of the species, 

 and simple tests as to whether a pigment is destroyed or not by strong 

 bases is not carrying the problem far enough, though the information 

 may have some value in differentiating arbitrarily between certain 

 species. 



Size and Shape — In nearly all genera of the Agaricales there is a 

 tremendous range in size of the fruiting bodies between those with the 

 largest and those with the smallest pilei, and nutritional differences 

 may account for great variation within many species. Within broad 

 limits, however, size of pileus has some taxonomic significance. In 

 many Hygrophori the pilei vary from 2-5 cm in diameter and in a few 

 they measure 3-12 mm. Going in the other direction, in H. sordidus and 

 H. pudorinus var. fragrans the pilei may measure 20 cm or more broad, 

 and a number of species have a range between 8-15 cm, i.e., H. russula, 

 H. subsalmonius, H. purpurascens ( occasionally 20 cm or more broad ) , 

 H. ponderatus, and H. tennesseensis. In general the species with large 

 pilei are found in section Hygrophorus. 



The shape of the pileus, especially at maturity, is often of taxo- 

 nomic value. Generally in the larger species the pileus is convex but 

 gradually expands to plane or merely plano-convex. In a few species 

 the disc is depressed to umbilicate or the cap may become infundibuli- 

 form. In some species it may remain umbonate. In some the pileus is 

 sharply conic when young and merely expands to broadly conic or 

 plane with a sharp conic umbo in age. In those species in which the 

 pileus is notably depressed, or acutely umbonate to conic, taxonomic 

 use is made of the character. The separation of series Conici in Hygro- 

 cybe is an example of such use. 



Surface Characters — The characters of the pileus surface which 

 are, or may be, of importance in species diagnosis include whether or 

 not the cap is glabrous, fibrillose, or scaly; whether it is dry, moist and 

 hygrophanous, lubricous, viscid, or slimy; whether the margin is even 

 or striate; and whether veil remnants are visible along the edge. 



