OBSERVATIONS ON PEZIZA. 
IDO 
in conjunction with other variations. Because, in the greater 
number of instances, the same species is not found in such diverse 
habitats. Usually a terrestrial species, such as Peziza rutilans is 
absolutely confined to soil, but instances are not unknown, as in 
Peziza scutellata, where the same species may occur as well on 
rotten wood as on naked soil, or Peziza hepatica , where the same 
species may be found on dung as well as on the earth. Exceptions 
of this kind are sufficiently rare to enable us to include the habitat 
as one of the minor considerations which have to be taken into 
account. 
2. Dimensions. The average size of a species is usually indicated 
within limits to which the individuals are found to conform. 
Although the beautiful Peziza aurantia under ordinary circum- 
stances reaches from one to two or three inches in diameter, yet the 
same species has been found growing under conditions in which the 
largest individual did not exceed a quarter of an inch. Neverthe- 
less should such a species as Peziza scutellata, which is usually less 
than a quarter of an inch, be found attaining a diameter of two 
inches, such a circumstance would at once lead to an enquiry 
whether such a form could be the same species. All other condi- 
tions being equal, the same rule must apply to Peziza scutellata as 
to Peziza aurantia, notwithstanding that a dwarfed form of a large 
species is much more probable than a much increased form of a 
minute species. As with habitat, so with dimensions, a difference, 
however great, cannot be considered of itself as possessing specific 
value. 
3. Form. Nothing is more variable than external form, which is 
subjected to influences of many kinds, and particularly to the con- 
ditions and circumstances under which the plant is developed. Yet 
the departure is seldom so great as to obliterate the character of 
the original type. In appreciating form as an element of classi- 
fication, perhaps the most useful feature to regard is the presence 
or absence of a distinct stem. Distinctly stipitate species are seldom 
entirely sessile, probably never. Such species as Peziza macropus 
without a stem would be as rare as a white crow. In the minute 
caulicolous species there is often some difficulty in determining the 
exact limit between stipitate and sessile, but in the larger species 
this difficulty is seldom experienced. It is somewhat doubtful 
whether the presence or absence of a stem may not have a some- 
what exaggerated importance in the Friesian arrangement. Under 
any circumstances the stem, being merely the axis of the vegetative 
system, can only be of secondary importance. Stipitate species 
will, if covered or obstructed, elongate the stem considerably in the 
efforts made by the cup to expose its disc to the light. In like 
manner when growing on a plane surface, and in full light, the 
stem will be much abbreviated. This may be well observed in P. 
coccinea , which from its habit of growing on sticks in old hedges 
has often to struggle for existence under difficulties. Apart from 
the stem other modifications of form seem to us too unstable, 
