Genus Ner audio. — -Cowan 
235 
Neraudia has been a problem of this sort and it 
is apparent that instead of very precise, definite, 
constant characters which operate throughout 
the genus, there is a tendency for differences to 
be expressed in sets of characters. Furthermore, 
a character which is constant in one group may 
prove to be quite variable in another. Each 
population is influenced by its own set of en- 
vironmental factors and each has its own par- 
ticular genetical makeup. These two sets of 
factors alone are enough to insure that the degree 
of variability and the organ affected may be 
quite different in each population. 
Leaf shape has been used to distinguish some 
of the groups in this genus and is occasionally 
a usable character since some of the groups show 
tendencies toward particular leaf shapes. How- 
ever, in most of the groups leaf shape exhibits 
so much variability that it is not satisfactory as a 
key character. In some groups ovate to elliptic 
leaves with intermediate shapes occur in the 
same collection; in such groups, at least, leaf 
shape is an unreliable character. Leaf size is 
expected to show some variation in all genera 
but in this genus the extremes of lengths and 
widths are often great in the same group. The 
shape of the base and of the apex of the leaves 
is often more constant but this is not a com- 
pletely reliable key character either. 
Vesture of the leaves has proved the most 
reliable character in the genus and is, I believe, 
genetical in nature. Even the quantity of pubes- 
cence present seems to be relatively constant; 
but it is the type of hair, distribution, posture, 
and orientation of the hairs that are used as 
key characters. The hairs are always simple but 
may be short and uncinate, longer and arcuate, 
curving and bending irregularly, or straight. In 
some groups the lower leaf surface is glabrous 
or sub-glabrous; in others the pubescence is 
restricted to the venation but in most groups 
this is not so. The pubescence on the upper leaf 
surface is always of the same type as that below 
but is more sparse and usually appressed. The 
consistency of the leaves varies somewhat, inso- 
far as it has been possible to observe it in fresh 
and dried collections, but it is constant enough 
to be used in identifying some groups. 
The venation of the leaves is of two general 
types and on this basis the genus is separable 
into two parts. If a leaf is held against a strong 
light the fine details of the venation are clearly 
discernible with or without magnification. Be- 
cause of the prominence of the secondary vein 
branches the first type appears to be a coarse- 
meshed net within the intervals of the primary 
vein branches, whereas the second type, due to 
the equal or greater prominence of the tertiary 
TABLE 3 
Distribution of Species and Varieties of Neraudia. 
KAUAI 
OAHU 
MAUI 
LANAI 
MOLOKAI 
HAWAII 
N. melastomae folia 
var. melastomae folia 
X 
.. 
- 
-- 
var. uncinata 
.. 
X 
.. 
.. 
.. 
var. Gaudichaudii 
X 
.. 
.. 
.. 
var. pubescens 
X 
.. 
var. parvifolia 
X 
var. pallida 
.. 
X 
N. angulata 
var. angulata 
.. 
X 
.. 
.. 
var. dentata 
X 
N. kauaiensis 
var. kauaiensis.... 
X 
var. Helleri 
X 
__ 
.. 
N. ovata 
.. 
.. 
.. 
X 
N: sericea 
X 
X 
X 
Total number of groups 
per island 
3 
6 
2 
1 
1 
1 
