358 ATKINSON— GALERULA IN NORTH AMERICA. 



has a cartilaginous rind; in the young stage the margin of the pileus 

 is straight, lying parallel with the stem, i. e., the margin not being 

 incurved; a distinct veil is usually absent, or if present it is not 

 usually of sufficient tenacity to form a distinct annulus on the stem. 

 This feature of the straight pileus margin is often difficult to deter- 

 mine, since, in many cases, the number of individuals of a species 

 collected is often too few, and they are in a too advanced stage of 

 development to determine the relation of the pileus margin to the 

 stem. Nevertheless, to one possessing some familiarity with the 

 genus, the external form or " habit " of the plants, taken in con- 

 junction with their color, serves in a large number of cases as a 

 reasonably sure provisional means of differentiation from the related 

 genera. 



In some well-recognized species of the genus, however, the 

 margin of the pileus is incurved in the young stages and never be- 

 comes straight. A notable example is Galernla angusticcps. Fur- 

 thermore, there appear to be structural characters of great impor- 

 tance wdiich indicate that certain species with a convex pileus, or a 

 few with the margin incurved when young, are more closely related 

 to the Galernla type than to other types, for example, certain species 

 which, on the basis of the "habit" principle would fall in the genus 

 Nancoria, Phitcolns, or even Hebeloma; while a few species placed 

 in Galernla because of the " habit " formula, are excluded when the 

 morphological, or structural, principle is employed as the basis of 

 determining relationships. 



On the basis of the morphological principle the species can be ar- 

 ranged in two groups. First, those in which the pileus is homo- 

 geneous, and second, those in which the pileus is corticated. This prin- 

 ciple of grouping the species was, in fact, employed a quarter of a 

 century ago by Fayod- who carried the principle still further by 

 recognizing two generic concepts. He recognized Conocyhe for the 

 species with a corticated pileus, and Galcra for those with a homo- 

 geneous pileus. 



In his concept of the genus Conocyhe, the cortex of the pileus 

 was merely indicated as " pseudoparenchymatous." This definition 



- Fayod V., " Prodrome d'une liistoire naturelles des Agaricines," Ann. 

 Sci. Nat. Bot., VII., 9: 181-411, 1889. 



