236 
PACIFIC SCIENCE, Vol. Ill, July, 1949 
branching gives the impression of a very fine- 
meshed net. The principal veins and their first 
branches may be strongly salient or only slightly 
raised. The leaves may be either palmately 
nerved or triplinerved and this character is of 
some use in distinguishing certain groups. 
The flowers are of two sexes borne on separate 
plants. Flowers of either sex may be sessile or 
short-pedicelled but are constantly either one 
or the other. The calyx of all pistillate flowers 
is fused so that the ovary is loosely enclosed 
in the inflated calyx. The tip of this perigynium 
is always elongated into a beak through which 
the style passes. The stigma is filiform and 
covered more or less completely with stout stig- 
matic hairs which serve as receptive surfaces 
for the pollen. The pubescence on the exterior 
surface of the calyx is ordinarily of the same 
type and posture as that found on the lower 
leaf surface. After fertilization of the single, 
erect, basally attached ovule the ovary under- 
goes certain characteristic changes in form and 
becomes hard and bony. More striking though 
is the change in the calyx, which enlarges to 
many times its original size, becomes fleshy, 
and turns red at maturity. It is variable in 
shape and ranges in size from 3 or 4 millimeters 
to as much as a centimeter or more in height. 
The achene characters are used to distinguish 
species and groups of subspecific rank. The 
dimensions and shape of the basal and apical 
portions of the achenes are usable characters 
but only if completely mature forms are avail- 
able. The apical portion may be conic or de- 
pressed-conic and may be separated from the 
basal portion incompletely or completely by a 
deep or only slight constriction. The basal 
portion may be flattened or convex and its outer 
margin may be involute or plane. 
The staminate flowers and pistillate flowers 
may be borne on pedicels. When they are so 
borne the pedicels are slender-filiform but be- 
cause of their shortness (0. 5-2.0 mm.) are most 
easily observed at nodes where flowers and 
fruits have been shed. Occasionally the scars 
of fallen sessile flowers become somewhat 
swollen but differ from pedicels in their greater j 
thickness and shortness. 
The calyx of the staminate flowers consists | 
of four navicular lobes which separate at ma- 
turity to release the four, opposite, inflexed 
stamens. The filaments are folded inward so 
that the connective is nearest the center of the 
flower. At maturity the filaments, when released 
by the opening of the calyx segments, snap 
outward explosively and at the same time the 
pollen is discharged in a small white cloud. 1 
From this method of pollen discharge and the 
presence of the feathery stigma described above, 
it may be safely postulated that the pollination 
agent is the wind since both of these mechanisms j 
are adaptations for wind pollination. The stami- 
nate flowers have few distinctive characters 
other than different types of hair on the calyx 
and the consistency of the lobes. 
TAXONOMIC CATEGORIES 
Of all biological terms "species” is un- 
doubtedly one of the most difficult to define in a 
manner which is satisfactory and acceptable 
to even a small group of taxonomists. The 
concept itself is reasonably clear but the prob- 
lem of its definition must still be resolved by 
the individual worker. Each must decide what 
his basic criteria for the recognition of a species [ 
shall be and then attempt to apply his concept 
in the field as well as in the laboratory. Ex- 
perience and contacts with other taxonomists 
will usually force certain modifications of the 
original concept so that the ultimate interpre- 
tation may be quite unlike that originally held. 
In this paper a species is interpreted as a popula- 
tion of individuals showing constant morpho- 
logical differences distinct from those of other 
populations in the genus. 
Varieties are considered to be units within 
the main specific population which show a 
character or characters peculiar to themselves 
but these differences are often overlapping to 
some degree, i. e., varieties lack the distinctness 
which characterizes the specific unit. The 
varietal category has not been used to replace 
