(397 ) 
characters as well. There can be no question that the care- 
ful histological study of a large series of species, with special 
attention to the earliest stages and to development, would 
throw much light on their relationships. At present, how- 
ever, our knowledge of these characters, especially as far as 
our American species are concerned, is too limited to admit of 
broad generalizations. It is my belief, also, that histological 
characters of importance will in nearly all cases be found to 
be correlated with recognizable macroscopic differences. 
Hennings in the Pfanzenfamrlien, while he has recognized 
a considerable number of tribes or subfamilies, has not kept 
pace with the modern tendencies in the matter of genera, 
but tends to revert to the complicated system of a few large 
genera with many subgenera and sections. His generic 
names have been chosen, too, according to a system which 
is quite incomprehensible. 
In seeking for a character to use as the primary dividing 
line for the grouping of the genera belonging to the great 
tribe Agariceae in arranging the following key, the presence 
or absence of a membranous organ covering the young 
lamellae has finally been chosen, thus grouping them in two 
series, Gymnophylli and Cryptophylli. This seeming inno- 
vation is in reality only a return to the original basis of 
classification first proposed by Persoon. It is not fully 
satisfactory and results in the separation of some evidently 
related groups. Part of such old genera as Trecholoma, 
Hebeloma, Flammula, Coprinus and Lentinus will be found 
in each of these series. There can be little question that the 
genus Leucomyces (usually known as Amanita) with its basal 
cup-like volva formed from the universal veil, and its well- 
marked annulus formed from the partial veil or cortina, rep- 
resents the highest and most complex type to be found among 
the gill fungi. It should be noted that here the young 
lamellae are protected by two clearly distinct membranes, 
each of which has unfortunately been called a veil. In this 
discussion this term will be retained for the outer or universal 
covering, while the inner or partial one will be referred to as 
the cortina. Since these membranes thus mark the highest 
