Atoll Vegetation — FOSBERG 
Fig. 5. Inner beach on Mejat’to Islet, Jaluit Atoll, 
Caroline Islands, showing Cordia suhcordata tree and 
herbaceous vegetation. PHOTOGRAPH BY F. R. FOS- 
BERG. 
On the sandy inner shore, or lagoon beach, 
is a narrow strip of scattered trees such as 
Cordia suhcordata , Hernandia ovigera, Termi- 
nalia catappa, Barringtonia asiatica , Thespesia 
populnea, and, in rocky places, Pemphis acidula: 
Here also are such sand-loving herbs as Vigna 
marina, Triumfetta procumbens, Thuarea in- 
voluta, etc. 
Fig. 6. Village scene on Ebon Atoll, Marshall 
Islands, showing Carica papaya, Crinum asiaticum, 
and other cultivated species. Papaya showing chlo- 
rosis. PHOTOGRAPH BY LEONARD E. MASON. 
91 
In general the indigenous flora of atolls is 
more meager to the eastward in the Pacific, 
richer in the west, as would be expected from 
the isolation of those in the east and the prox- 
imity of the western ones- to large islands with 
their complex floras. 
The introduced flora, both wild and culti- 
vated, is extremely limited. The wild introduced 
species are mainly shallow-rooted herbs. It was 
the cultivated flora that offered the original 
clue to the distribution of atoll vegetation. It 
was noticed that, though numerous species have 
been tried out, both by the plant-loving natives 
and by residents of foreign origin, relatively few 
of them have survived. Still fewer can be con- 
sidered successful even under the protection and 
cultivation of man. Those that survive, but are 
not especially successful, show, without excep- 
tion, signs of a severe localized chlorosis (yel- 
low coloring) of the type usually associated 
with excessive sodium, with resultant deficiency 
of assimilated potassium and a more general 
chlorosis possibly associated with deficiencies 
of other ions due, perhaps, to high pH. Lantana 
camara, ordinarily a most aggressive weed, is 
yellow and sterile where planted in the Marshall 
Islands. Even some of the species, such as the 
papaya, which survive and reproduce them- 
selves, are often chlorotic. Also these species are 
much more successful toward the center of an 
islet where the salinity is naturally lower. Very 
few of the introduced plants, excepting those 
which are themselves strand plants with a tol- 
erance toward high salinity, or those which are 
shallow-rooted, thus living in the upper layers 
where the salt is to some extent leached out by 
rains, have succeeded in becoming naturalized. 
That there is a high water table in this type 
of island is shown by the numerous wells only 
a few feet deep, dug by the natives. The water 
is ordinarily more or less brackish. Hence it 
is not reasonable to suppose that the sparseness 
of woody vegetation of the drier islands is due 
to actual physical lack of water, since the tree 
roots can undoubtedly go down to the water 
table. Physiological dryness resulting from high 
