Ecology of Marcus Island-— SAKAGAMI 
85 
and atolls. Its minute size and the poor con- 
servation of water by coral sand may be the 
main causes of the dry climate of Marcus, as 
in Wake Island with a similar topography and 
climate. Consequently, the climate of Marcus 
is, in spite of its subtropical position, inadequate 
to support a luxuriant flourishing of organic 
and ecological diversities. (Rain is the only 
source of fresh water in the island.) 
FLORA AND VEGETATION 
The flora of Marcus has been reported by 
Yabe (1902), Bryan (1903), and Tuyama 
( 1938). The plants collected by me were kindly 
determined by Dr. Tuyama. They are listed in 
Table 2, together with those reported by the 
earlier publications. Comparison of the present 
flora with those of previous studies will be dis- 
cussed later. Here the discussion is limited to 
the plants collected by myself. Judging from 
the size and topography of the island, I believe 
that the collection of the plants which were 
growing there during my stay is almost com- 
plete. It is obvious from Table 2 that the flora 
is extremely poor both in number of species 
and in endemism. Most of the species are 
either cosmopolitan or tropicopolitan, or are 
those which behave as dominants in many com- 
munities because of their great vigor. In other 
words, we find here no more than a typical 
example of the poor flora of oceanic atolls. 
The structure of the vegetation, too, is very 
simple. The arboreal stratum was composed of 
M esserschmidia and Pisonia mixed in an ap- 
proximate ratio of 7:3, although the latter was 
relatively scarce outside the E. triangle (Figs. 
1, 4). The density and resulting coverage was 
highest in the E. triangle and next highest along 
an abandoned road in the northern section of 
the NW. zone. In addition to these two dom- 
inants, about a dozen papayas were observed 
TABLE 2 
Synoptic Table of Plants Recorded from Marcus Island 
SAKAGAMI 
YABE (1902) 
BRYAN (1903) 
TUYAMA (1938) 
(Identified by Dr. Tuyama) 
Species recorded at least in two occasions 
Tounefortia argentea 
Tounefortia serviced 
Messerschmidia argentea 
Messerschmidia argentea 
Cocos nucifera 
Cocos nucifera 
Cocos nucifera 
Cocos nucifera 
Morinda citrifolia 
Rubiaceae gen. sp. 
Morinda citrifolia 
Carica Papaya 
Carica Papaya 
Pisonia grandis 
Pisonia grandis 
Portulacea oleracea 
Portulacea lutea 
Portulacea oleracea 
Portulacea oleracea 
Tobacco 
tobacco 
Nicotiana Tabacum 
Boerbaavia repens 
Boerbaavia repens 
Ipomoea pes-caprae 
Ipomoea pes-caprae 
Eleusine indica 
Eleusine indica 
Species recorded only once 
Graminae gen. sp. 
Euxolus sp. 
Dactyloctenium aegypticum 
Bryophyllum pinnatum 
Panicum pruriens 
Setaria lutescens 
Pennisetum setosum 
Rottboellia sp. 
Syntherisma sangunalis 
Cenchrus ecbinatus 
a low trailing herb 
Scaevola frutescens 
Erigeron sumatrensis 
Malvastrum tricupidatum 
Euphorbia hirta 
an unknown herb 
Lepturus repens 
E. prostrata 
Sonchus oleraceus 
Boerbaavia diffusa 
