Vegetation and r?j q: \ stok Island 
by t t Lor g 
The flora of Vostok Island consists of two species of vascular 
plants, Boerhavla repens L. and Pisonia grandis L. (Fosberg, 1937)- 
Collections of these species were made in 1935 by W. J. Anderson and 
in 1965 by C. R. Long. These collections are summarized below. The 
sheets are filed at the B. P. Bishop Museum and the University of 
Hawaii. 
»/ 
na c e a e 
Boerhavla repens L 
■ — , - ,, I I ,■■■.-■■ „ - . .... »n. — 
Anderson s.n. 
3204 , 3208 (uh). 
(bish) 
& r- 
a v: 
.a diffusa; Long 3L9t, 3202, 3203, 
Pisonia grandis E. Br 
Anderson s.n. 
(bish). 
Long 71 92 (UH). 
The island remains much as ierson reported with a dense growth 
of Pisonia trees to approximat l.y 20 m. high. Towards the middle of the 
island are random clearings w. nick layers (to .35 m.) of decayed 
leaves and wood. On the sandy gas of these clearings several Boerhavla 
plants were observed. Several excavations were made in the open areas 
and under the canopy. Underlying the humus was a phosphatic hardpan 
which was very friable in the top layers. The high branches of the 
Pisonia were used by the Great Prigatebird as nesting sites. Some of 
the upper branches were bare in the vicinity of the nest sites due per¬ 
haps to the activities of these birds. On the north and east sides of 
the island were open coral sand and rubble with Boerhavla in vigorous 
masses. This site was used by nesting Blue-faced Boobies ( Sula dactylatra ). 
This strip of low vegetation varied from 3 to 20 m. in width. An inten¬ 
sive search of the island failed to reveal other plant species particularly 
the Portulaca reported by Bryan ( 19 ^ 2 ). The Polynesian rat was common 
within the forest canopy. It may be that the Portulaca is eaten by this 
species. 
At the southwest end there is an outcrop of consolidated beachrock. It 
seems highly probably that both of the native species were introduced by 
birds as the seeds of both are sticky and thus easily transported. No 
evidence of Pisonia seedlings was found but numerous sprouts from fallen 
trunks and exposed roots were seen. Binoculars were used to scan the upper 
branches but no fruits were observed. Along the west side areas of eroded 
soil and newly deposited sand were observed. This evidence together with 
the clearing in the center of the island probably indicates high wave action 
prior to the visit of the Pacific Project party in June 1965 * Sea water and 
heavy rains probably seep through the porous central area which is at a 
lower elevation than the beach crests and inner slopes. 
The areas beneath the Pis or. ..a canopy are devoid of vegetation with the 
exception of crusts of bluegree. algae which cover the soils suriace, 
rotting trunks and coralline boulders. No thick recent guano deposits were 
observed on the soil surface under the canopy. The humus depths vary under 
