90 
extensive Lepturus— Messer schmidia savannah 
on dry Christmas Island, the dense moist forest 
of Nomwin, the tangled swamp on Ailing- 
lapalap, or the solid forest of a single species 
on isolated Vostok Island ( Bishop Mus. Spec. 
Publ. 30: 19, 1936). 
On most atolls may be seen a very definite 
vegetational zonation. This varies on different 
atolls, but a certain order is usual, oriented con- 
centrically from the outer beach to the inner, 
or lagoon, beach. 
The outermost zone is a scrub, principally of 
Scaevola frutescens, reaching a height of 2-5 
meters and often mixed on its inner edges with 
Cordia subcordata and Soulamea amara. On very 
narrow islets and spits between islets this may 
extend the full width of the islet. In sandy soil 
Smiana maritima may be an important com- 
ponent. 
Next inward there is usually a halophytic 
forest zone of the tree heliotrope ( Messer - 
schmidia argentea ) and Pandanus. In some re- 
gions, as in the Marshalls and Carolines, Ter- 
minalia litoralis is commonly found in this 
forest. This is ordinarily a rather narrow belt. 
The greater part of the interior of an islet is 
usually occupied by a more mesophytic type of 
forest. At the present time on most atolls this 
is largely made up of coconut plantations, which, 
contrary to popular opinion, are not the natural 
vegetation of atolls but are planted by man. 
In places on the wetter atolls the coconuts are 
partly replaced by breadfruit trees which occa- 
sionally reach enormous size, towering above 
the coconuts and making a dense shade. Pan- 
danus is also common among the coconuts. 
Where scraps of the original vegetation of 
this zone remain they are found to be composed 
of such trees as Pisonia grandis, Pandanus spp., 
Ochrosia parviflora, Pip turns argenteus, Hibis- 
cus tiliaceus , Messer schmidia argentea, Calo- 
phyllum inophyllum, Barringtonia asiatica, Eu- 
genia sp., and others. On the drier islands the 
buka ( Pisonia grandis) tends to be dominant. 
In the interior of this zone there are fre- 
quently swales, marshes, ponds termed "man- 
PACIFIC SCIENCE, Vol. Ill, January, 1949 
Fig. 3. Interior of Hare Islet, Kapingamarangi 
Atoll, Caroline Islands, showing undergrowth in coco- 
nut-breadfruit forest, with ground cover of Steno- 
taphrum subulatum. PHOTOGRAPH BY F. R. FOSBERG. 
grove depressions” (see Fosberg in N. Y. Bot. 
Gard., Jour. 48(570): 128-138, 1947), or 
even fresh- water lakes, as on Washington 
Island. Here may be found sedges, grasses, 
and in the western Pacific, several plants of the 
mangrove formation. In the interior of this 
zone on the larger islands, the natives often 
excavate areas down to the water table, fill 
them with vegetable debris which decomposes 
to a muck, and therein plant taro (Colocasia ) , 
puraka ( Cyrtosperma ) , and other cultivated 
plants which do not thrive on the normal atoll 
surface. 
Fig. 4. Large excavated puraka patch surrounded 
by coconuts, showing sugar cane mixed with Cyrto- 
sperma chamissonis, Nukuoro Islet, Nukuoro Atoll, 
Caroline Islands. PHOTOGRAPH BY F. R. FOSBERG. 
