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PACIFIC SCIENCE, Vol. XXII, July 1968 
high precipitous cliffs. The southerly outer 
slopes of the main cone have been eroded into 
several steep valleys, presumably by intermittent 
streams. Bryan (1935) and Richardson and 
Fisher (1950) have given brief but detailed 
descriptions of the island. Its physical features 
have not changed appreciably in historic times. 
The island has suffered few attempts by man to 
use or modify it for his own purposes. Plowever, 
the introduction of rabbits at some unknown 
date prior to 1900 and the establishment of 
exotic species of plants have undoubtedly 
changed the original vegetation. In World 
War II Manana was used as a bombing and 
strafing target (Green, 1942). Small shells are 
still found occasionally in its loose soils, al- 
though the Navy Department has made some 
effort to remove these potentially dangerous 
missiles (Woodside, personal communication). 
Because of its easy access, Manana may have 
been occupied frequently as a fishing station by 
the Hawaiians. Records of visits for the purpose 
of studying the flora and fauna are relatively 
few. Bryan (1935) reported on insects, vegeta- 
tion, and miscellaneous topics; Munro (1945, 
1950) briefly described the vegetation. Richard- 
son and Fisher (1950) made repeated observa- 
tions on its birds for nearly two years, and also 
published a list of plants. Other notes, mainly 
on birds, have accumulated over the years from 
the excursions of the Hawaii Audubon Society 
and have been published in their official journal, 
the Elepaio. 
FLORA AND VEGETATION 
Collections of plants made on Manana on 
several occasions provide some information on 
changes in the flora during the past 40 years 
(Table 1). A thorough search of the Bernice P. 
Bishop Museum herbarium has revealed no 
specimens from Manana collected earlier than 
1927; therefore no record is available of the 
island’s flora before the introduction of rabbits. 
The earliest published information was supplied 
by Bryan (1935). He reported that Marie C. 
Neal had compiled a list of 21 species of higher 
plants from Manana during four trips up to 
August 1934, but he mentioned only 8 of these 
species by name in his account. However, 18 
species are represented in the 1930 and 1934 
collections. 
In all, 28 species of higher plants have been 
found growing on Manana, and at least 18 of 
these were present at the time of our survey in 
1964. Richardson and Fisher (1950) reported 
only 7 of these 28 species. It is likely that others 
were actually present, for they did not consider 
their list as necessarily complete. Of the 7 plants 
listed for 1950, none is a native Hawaiian 
species, while 3 of the 18 found in 1964 are 
native. 
Munro (1945, 1950) discussed conditions on 
Manana between 1937 and 1941, and noted that 
the soils which have developed on the western 
slopes of the island and on the crater floor 
supported a "heavy cover’’ of introduced grasses 
and weedy herbs. He noted that the coconut 
trees were very small in 1941, but he did not 
give the date of planting. Richardson and 
Fisher (1950) indicated that the vegetation 
began to dry up in late May or early June, and 
by July all the vegetation was "brown and 
sear.” 
The most heavily vegetated parts of the island 
in 1964 were the floor of the main crater and 
the outer gentle slopes on the southwestern side 
of the island. In both places a fairly deep rich 
soil has developed from the decomposed tuff 
mixed with guano. On the upper south slopes, 
the upper inner slopes of the main crater, and 
the outer slopes on the north, east, and west, 
little or no soil has accumulated except in 
scattered pockets and cracks in the tuff, and few 
plants are present. The failure of soil to develop 
on these slopes is probably related to their 
steepness and their exposure to strong trade- 
winds. As the tuff decomposes in these areas, it 
falls or is blown away, either to lower vegetated 
areas or into the sea. 
The vegetation of the crater floor (Fig. 2) 
consisted mainly of Trichachne insularis, a bunch 
grass about 1 meter tall, and Nicotiana tabacum, 
an erect herb from 1 to 2 meters tall. Scattered 
here and there were Lycopersicon esculentum, 
Ageratum conyzoides, Boerhavia diffusa, Setaria 
verticillata, and Cenchrus echinatus. A few 
plants of Portulaca oleracea were found in the 
eastern portion of the crater floor, and one large 
shrub of Sida cordifolia grew near the northern 
edge of the crater floor. About 30 trees of 
