I'll) iah.i \) \\/> ( i LSS/J k \i k >\ 



scopic characters. It is such similarities as this that have in pari caused 

 us not to recognize these sections as separate genera. Closel) related 

 genera separated 1>\ a single character arc weak genera at best. 



However, when most species ol section Hygrophorus are com* 



pared with most of those in section HygTOCtjbe a number ol obviOUS 



differences stand out as indicated in our taxonomic data. The prob 



lein of evolution and relationship is thus reduced to a discussion ol how 



readily bilateral trama on the one hand and parallel trama on the othei 

 can be derived From the primitive interwoven type. We believe that 



this is not such a difficult change as may appear at first glance. 



In the first place the term "interwoven hyphae" actuall) is not in- 

 dicative of an homogeneous condition throughout CamarophyUopsis. 

 In some species, such as //. borealis, the gill trama hyphae at maturit) 



are up to 14 /x broad. In //. cremicolor these hyphae are very narrow 

 (1.5-3 fx broad). For most species the hvphal cells are 1-12 /< in diame- 

 ter and may be of equal diameter throughout or somewhat enlarged. 

 In such species as Hygrophorus colemannianus the hyphae of the 

 hymenopodial zone are actually subparallel, with the ramose subhyme- 

 nium a narrow zone to the exterior on either side. All that is needed 

 here to arrive at a type of hvphal arrangement very common in the 

 hymenophore of an Hygrocybe is lor the central interwoven bod) oi 

 the gill trama to become reduced in extent and the subparallel an an La- 

 ment of the hymenopodial area to become better developed. No ap- 

 preciable change in the genetic mechanism of the species need be 

 postulated to produce such a change. From this point forward it is a 

 simple progression to the typical kind of parallel gill trama such as that 

 found in H. coiiicus, where the central strand has been obliterated and 

 the subhymenium arises directly from the parallel hyphae of the hy- 

 menophoral tramal body. Tin's appears to be a simple progression eas- 

 ily accounted for genetically, and it is not clear that "parallel* vs, in- 

 terwoven" gill trama can be a character sufficiently significant to base 

 a genus on it. It is well known that hvphal diameters and hvphal ar- 

 rangements change markedly from youth to old age in a single species 

 so that at most the character is one in which considerable* latitude in 

 interpretation must be allowed for in all except the most distinctive 

 types, i.e., such as the inverse type characterizing the Volvariaceae. 



We may now examine the possible origin of the bilateral type of 

 gill trama found in section Hygrophorus. In many species ol section 

 Hygrophorus it is possible to demonstrate 1 that the hvphae diverge 

 from a thin to a distinct strand of interwoven hyphae extending down 

 ward and finallv toward the subhymenium. One of the 1 problems ol 

 working with dried specimens is that in a tew instances we have 



