124 MR. GEORGE MASSEE ON THE THELEPHORE E. 
cylindrical with only two sterigmata, others, again, only slightly 
or not at all thickened upwards, and bearing at the attenuated apex 
a single spore (gonidium). Hence the distinction between the 
Hymenomycetes and the Hyphomycetes, according to the present 
state of knowledge, depends on the presence or absence of a 
purely arbitrary and preconceived conception as to what consti- 
tutes a basidium. Every other character being equal, as is the 
case in numerous instances, the presence of the clavate tetra- 
sporous basidium in the hymenium, irrespective of the presence 
of an equal number of unisporous basidia (gonidiophores), proves 
the plant to be a Hymenomycete, whereas if the latter are alone 
present, but not thickened upwards, whether monosporous or 
polysporous, the plant must be considered as a Hyphomycete. 
In typical Hymenomycetes the basidia and accompanying 
structures form a compact, continuous hymenium, but to this 
rule there are numerous exceptions in the Thelephoree. 
It is not unusual to meet with specimens of Corticium arach- 
noideum spreading over mosses or decayed vegetable matter as a 
delicate, white, cobweb-like film not at all felted, the hyphe 
giving origin to scattered, erect, spore-bearing branches, the 
whole structure resembling under a lens such Hyphomycetes as 
Dactylium macrocephalum ; but in this instance, although there is 
no approach to a normal hymenium, the basidia are typical, and 
the same specimen on passing to a solid substratum of bark or 
wood may produce a dense subiculum covered with a compact 
waxy hymenium. The same thing may be met with in Peniophora 
velutina, Corticium sulphureum, aud other species with a byssoid 
radiating mycelium ; consequently the second leading character of 
the Hymenomycetes, the compact hymenium, fails at the tra- 
ditional point of junction with the Hyphomycetes. A third 
character of importance in distinguishing between the Hymeno- 
mycetes and the Hyphomycetes is the presence in the former of 
a compact hymenophore, which often presents a pseudo-paren- 
chymatous structure in section, due to the closely compacted 
byphe being agglutinated together, whereas in the Hy phomycetes 
the basal stratum normally remains loosely fibrillose ; but there 
are exceptions in both families. 
The diagram on p. 125 illustrates the morphological relation- 
ship between the various genera of the Thelephores, and also 
the points of departure of the remaining orders of the Hymeno- 
mycetes, the accompanying bracketed genus being considered as 
