222 
PACIFIC SCIENCE, Vol. XIX, April 1965 
dence for this is inconclusive and may be inter- 
preted in other ways. There is, however, within 
the Pacific fern floras a distinctive southern 
element which may in part be of recent origin. 
The genus Polystichum is a member of this 
group and is best developed in New Zealand 
and eastern Australia, but it extends north- 
ward into the Society Islands. One species is 
completely circum-polar and related or similar 
species occur in temperate South America. 
Asplenium obtusatum Forst., or species very 
like it in both form and habitat, also occurs 
widely around the subantarctic extending 
north into eastern Polynesia. The present range 
in the colder parts of the Southern Hemis- 
phere and the extreme polymorphism of this 
group suggests a recent origin. To this south- 
ern group probably also belong several New 
Zealand species of Blechnum, including those 
of the B. procerum complex, and some species 
of Grammitis. Only one other species, Hymen- 
ophyllum ferrugineum Colla, is common only 
to temperate South America and New Zealand. 
This is a much slighter relationship than could 
be expected if Copeland’s theory of an ant- 
arctic origin were acceptable, even more so 
when the much-discussed similarities between 
the phanerogams are compared with it. 
ISOLATED ISLANDS 
It may be of interest to examine the floras 
of a number of South Pacific islands which are 
sufficiently isolated not to belong to any group. 
Pitcairn Island at the extremity of eastern Poly- 
nesia has a fern flora of only 19 species, all of 
which are similar to or only doubtfully distinct 
from those of the Society and Austral Islands 
(Brownlie, 1962^). This appears to be a re- 
cent flora with little or no time for local dif- 
ferentiation, and with none of the distinctive 
species of the nearest groups included. Pre- 
sumably these species which have succeeded in 
colonising the most south-easterly extension of 
Polynesia are among the most successful in dis- 
persal of the Malayan-Polynesian ferns. 
Rotuma Island, an isolated volcanic cone 
northwest of Fiji, has a fern flora consisting of 
26 species (St. John, 1954). Again, most of 
the species are those of wide distribution in 
the tropical Pacific with one endemic, Clyco- 
sorus rotumaensis St. John, closely related to 
Fijian species, and one, Tectaria dimorpha St. 
John, whose relationships appear doubtful. 
This latter belongs to a group much in need 
of complete revision in the Malaysian-Pacific 
area. The most obvious similarities of the whole 
flora are with Fiji and the New Hebrides. 
Norfolk Island, although closer to New Zea- 
land and with many ferns in common with 
that country, also has several species more ob- 
viously belonging to eastern Australia. Of the 
total of 38 species noted by Laing (1915) only 
three or four are endemic, the remainder being 
either widespread Pacific species which occur 
also in Australia, or definite Australian repre- 
sentatives. The almost complete Australian re- 
lationship of the flora suggests long range wind 
dispersal as the most likely mode of arrival. 
Lord Howe Island, due to its greater altitude 
and consequent variety of habitat, has a some- 
what larger flora than Norfolk Island (Oliver, 
1917) but here again the relationship is pre- 
dominantly with the Australian mainland. There 
is, however, a suggestion of a somewhat older 
group shown by the endemic elaboration of the 
Hymenophyllaceae, a character lacking in the 
other isolated islands mentioned. This specia- 
tion in the Eu-Hymenophyllum and Meringium 
sections of the genus Hymenophyllum is other- 
wise confined to the older or larger areas, New 
Zealand, New Caledonia, eastern Australia, and 
to a minor extent Fiji. Another interesting fact 
is the doubtful distinction between Asplenium 
pteridoides Baker of Lord Howe and A. poly- 
phyleticum Compton of New Caledonia. It 
seems that the fern flora of Lord Howe is not 
merely one with an immediate relationship to 
the nearest source of supply, as is the case 
with Pitcairn, Rotuma, and Norfolk. 
DISCUSSION 
The outstanding impression of the whole 
fern flora of the South Pacific is that it is an 
extension eastwards of the one found in the 
Malaysian area, with a gradual reduction in 
numbers towards the east. This is most obvious 
if the islands to the south of the New Hebri- 
des are omitted. When New Caledonia and 
