2 
Massee—A Monograph of 
and in turn constitute the leading structural features of a new 
group. These numerous transitional species which hover round 
each group are respectively the sheet-anchor of the biologist 
and evolutionist, and the bane of the old-school systematist. 
The broad features of development in the two groups named 
above may be characterised as follows. In the Hymenomy- 
cetes the simplest genera, as Corticium and Peniophora , consist 
of a broadly effused undifferentiated sporophore attached by 
the whole of its under surface to the substratum, the upper or 
free surface forming a continuous even hymenium. From this 
primitive condition the modifications of the hymenial surface 
all tend towards one idea, that of exposing the greatest pos- 
sible area of spore-bearing surface in the least possible space, 
and evolving in the following ascending order : Thelephoreae, 
hymenium even, plane ; Clavarieae, hymenium even, sporo- 
phore club-shaped or variously branched; Hydneae, hymenium 
broken up into more or less flattened teeth or spines ; Poly- 
poreae, hymenium honeycombed or consisting of closely-packed 
tubes lined with basidia ; Agaricineae, hymenium spread over 
thin plates or gills arranged side by side and radiating from a 
central point. 
The progressive differentiation of the sporophore persistently 
aims at one object, that of concealing the hymenium until the 
spores are mature, a statement which is not in harmony with 
the general conception that in the present group the hymenium 
is from the first exposed. In the Thelephoreae, Clavarieae, 
and Hydneae the hymenium is exposed from the earliest stage, 
whereas in the Polyporeae and the Agaricineae the hymenium 
in the higher forms is completely differentiated while yet con- 
cealed by a structure known as the veil, which in many species 
is only ruptured by the expansion of the pileus when the 
spores are mature. The idea of concealing the hymenium 
from the light is equally apparent in the various orders 
enumerated, excepting the Clavarieae. In the Thelephoreae, 
as already stated, the simplest genera, Corticium , Coniophora , 
and Peniophora , have the hymenium covering the whole of the 
uppermost or free surface of the sporophore, and consequently 
