Flora of Johnston Island, Central Pacific 
F. R. Fosberg 1 
The first list of plants of Johnston Island, 
published in 1931 by Christophersen ( Vascular 
Plants of Johnston and Wake Islands. Bernice 
P. Bishop Mus. Occas. Papers 9(13): 1-20, 
1931), was based on the collections of the Tan- 
ager Expedition in 1923. Three species were 
reported and a few notes on the vegetation 
were included. The three species were Lepturus 
repens, Boerhavia diffusa, and T rib ulus cistoides. 
There is little doubt that these made up the 
whole vascular flora at the time, as Johnston is 
a very small, low, sandy, barren island and 
would not have been difficult to cover thor- 
oughly. Few smaller floras are known (see Fos- 
berg, F. R., Vegetation of Vostok Island, Central 
Pacific. Bernice P. Bishop Mus., Spec. Pub. 
30: 19, 1937). 
In the late 1930’s aviation activities began to 
change the island. It became an important air 
base during the war and when I paid it a brief 
visit during 1946 there was apparently no 
original vegetation remaining, the whole island 
being occupied by runways and buildings with 
disturbed ground in the open places and along 
paths and roadsides. The plant most noticeable, 
though not most abundant at that time, was 
Pluchea odorata. Doubtless this had been 
brought from Honolulu, where it is common, 
but whether it was introduced accidentally or 
deliberately is not known to me. A number of 
other plants were noticed growing as ornamen- 
tals around the buildings. 
On November 1, 1946, my brother, Kenneth 
P. Fosberg, made, at my request, a collection of 
all the plants that he could find during a day 
1 Research Associate, Pacific Vegetation Project, 
Catholic University of America, Washington, D. C. 
Manuscript received March 7, 1949. 
spent on the island. Twenty-six species in all 
were collected, most of them in duplicate. A 
coconut seedling was seen but not collected. An 
almost complete set of plants was presented to 
the Bernice P. Bishop Museum in Honolulu. 
The remainder were sent to Washington, but 
were apparently lost in the mail. 
The increase from 3 to 27 species consists 
mainly of species that are obvious introduc- 
tions, either deliberate, as cultivated plants, or 
accidental, as weeds. Only two, Messerschmidia 
argentea and Scaevola frutescens, are species that 
might be expected to be .native on an island 
such as Johnston, and they are both conspicu- 
ous enough so they could not possibly have 
been missed by the Tanager party if they had 
been present in 1923. The flora has thus been 
greatly enriched by human activity, and the 
original flora has maintained itself. This could 
be likely only in a pioneer habitat such as a 
dry coral island. 
All the weeds as well as the planted species 
are common on Oahu, Hawaiian Islands. 
Whether the weed seeds came with nursery 
stock or by accidental adherence to plane or 
cargo is hard to know; but observations around 
other Pacific air bases suggest that the latter 
process is not negligible. 
The list of species follows with such notes 
on occurrence as were provided by the col- 
lector. The general habitat for all is coral sand. 
Determinations are my own. 
Cenchrus echinatus L. Abundant. K. P. Fos- 
berg 7. 
Chloris inflata Link. Abundant. K. P. Fos- 
berg 11. 
Cynodon dactylon (L.) Pers. One small patch 
seen. K. P. Fosberg 16. 
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