58 
PACIFIC SCIENCE, Vol. V, January, 1951 
of ssp. St.-Johnii very similar to var. sand- 
wicense. 
On each island of the Hawaiian group 
independent modifications, some of which 
are superficially similar and have resulted in a 
sort of parallel evolution, have arisen in the 
populations. This curious phenomenon, 
which is characteristic of populations on 
some other Pacific islands as well, has been 
remarked on by Degener (1930: 266), who 
realized the independent origins of the hairy- 
leaved and ''peach-leaved” forms on the 
various Hawaiian islands. Even more per- 
plexing from the taxonomic point of view 
is the occurrence of reversions of characters. 
Thus, in tracing the character of style 
pubescence in the Polynesian species, we find 
that it is present in M. rapense, beginning to 
disappear in M. Stokesd, absent in ssp. 
Wilderi, but reappearing in ssp. St.-Johnii. 
Naturally this sort of behavior of morpho- 
logical characters introduces great hazards in 
classifying and interpreting the phylogeny of 
the Polynesian species. 
It is interesting that there seems to be 
little evidence of inter-varietal hybridization 
in the Hawaiian Islands. No indubitably 
hybrid specimens have been seen except 
possibly from the island of Hawaii, and here 
additional field work will be necessary to 
establish the actual hybrid nature of such 
specimens. The conclusion seems inevitable 
that evolution in Hawaiian Myoporum has 
been most strongly conditioned by geo- 
graphical isolation, while inter-varietal hy- 
bridization has not played an important part. 
The fast rate of differentiation and slow dis- 
persal rate of the populations have been 
acting together to produce an intense micro- 
evolution. The taxonomic difficulty of char- 
acterizing M. sandwicense is a reflection of the 
rapidity and recentness of this process. Within 
this one species can be found groups at all 
stages of differentiation — from individual 
variants to populations of almost specific 
distinctness. 
Owing to the ruination of much of the 
flora of the Austral Islands, our knowledge of 
the groups there is rather incomplete. Never- 
theless, it is clear that M. rapense is very 
closely related to M. laetum of New Zealand 
and is no doubt derived from it or a similar 
type. On Rapa and Tubuai it has changed 
little from the original immigrant, but on 
Raivavae it has given rise to and been almost 
supplanted by the polymorphic M. Stokesii, 
which itself is undergoing incipient speciation 
in the manner of M. sandwicense. 
SYSTEMATIC TREATMENT 
It is not pretended that the taxonomic ar- 
rangement which follows is definitive. Fur- 
ther collecting on some of the Hawaiian 
Islands may necessitate a reappraisal of some 
of the unnamed forms listed herein and 
should result in the discovery of additional 
forms and perhaps even new varieties. Ade- 
quate understanding of a highly polymorphic 
genus such as Myoporum requires accurate 
field observations, and careful notes by col- 
lectors concerning flower color and scent, 
fruit color, and leaf variation will be of great 
assistance in future studies. 
MYOPORUM Soland. ex Forst. f.. Prodr. 
44. 1786. 
Generic synonyms pertinent to the Poly- 
nesian species are: 
Pentacoelium Sieb. & Zucc., Abh. Akad. 
Muench. 4(3): 151. 1846. 
Polycoelium A. DC., Prodr. 11: 705. 1847. 
Prinastrum Nutt, ex Gray, Am. Acad. Sci. 
6: 53. 1866 (as synonym). 
Low or erect shrubs, rarely tall trees. Leaves 
alternate (rarely opposite), sessile or with a 
winged petiole, linear to lanceolate or el- 
liptic, entire or serrate, glabrous or rarely 
pubescent, often viscid when young. Flowers 
axillary, solitary or clustered, ebracteolate- 
pedicellate; calyx usually deeply 5-lobed, 
green and herbaceous, gland-dotted. Corolla 
usually 5-lobed, imbricate in the bud, sub- 
actinomorphic, campanulate to funnelform. 
