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PACIFIC SCIENCE, Vol. XVIII, October 1964 
the eastern coastal plain on West Maui. In 1962 
another population, 10 miles west of this area, 
near Ukumhame Shaft, was collected by Mr. 
Craig Whitesell. According to his notes, the 
population was scattered over 2-3 acres at 
about 250 ft elevation. This population was not 
located during the present study, but plants 
were found in the Pohakea Gulch region at an 
elevation of about 100 ft. These occurred under 
a thin cover of Prosopis immediately above a 
cane field and extending up into the gulch. 
Most of the dry area in the "saddle” of the 
island which is shown in Figure 1 is in cane 
cultivation. Judging by the habitat of tomen- 
tosum on the other islands, the only likely area 
for its occurrence on East Maui would be the 
dry southernmost region lying between Makena 
and Kamanamana Point. Its vegetation is com- 
posed principally of tall Prosopis scrub with 
frequent Opuntia, which is traversed in places 
by bare, or almost bare, lava flows. This area 
was visited but no tomentosum was found. 
5. Kahoolawe 
This island is uninhabited and has been used 
for some years by the U.S. Navy as a target for 
bombing practice. Its low-altitude location in 
the rain-shadow of Maui and a past history of 
heavy overgrazing combine to make it the most 
barren of all the major islands in the group. 
From the air it appears as a low plateau, prac- 
tically devoid of vegetation, with dry scrub lin- 
ing the steep gullies which surround its coast. 
Fifty years ago Forbes (1913^:7), on the last 
recorded botanical exploration of the island, 
found a population of tomentosum near the 
southwest end. 
6. Hawaii 
Three areas which would seem to offer appro- 
priate habitats for the establishment of the 
species were searched without success: 
(a) The dry coastal flats north of Kona Air- 
port, Kailua 
(b) The area bordering the coastal road be- 
tween Kealakekua Bay and the City of 
Refuge in the South Kona District 
(c) A small area between Honuapo and Pu- 
naluu Beach in the southern Kau District 
Time did not permit a visit to the Kau Desert 
and Hilina Pali areas which, as noted earlier, may 
have provided the necessary combination of alti- 
tudinal range and vegetational type for Mac- 
Caughey’s observations. 
CLIMATE AND "SOIL” 
The climatic conditions to which tomentosum 
is adapted would appear to differ rather sharply 
from those under which the wild forms of 
hirsutum flourish in the Caribbean. Honolulu 
weather records from 1948-1960 indicate that 
the average temperature on coastal Oahu varies 
(in round figures) between 70 and 80 F, with 
a mean of about 75 F, and a diurnal range of 
9 F. The winter (short-day) months tend to be 
cool and wet, though the monthly distribution 
of rainfall is very erratic. In contrast, the Carib- 
bean climate has a higher mean temperature, 
and short day length usually coincides with a 
pronounced dry season and cooler night tempera- 
tures. The Caribbean cottons grow vegetatively 
during the long wet days, and flower and set 
seed during the dry season. Flower initiation 
seems to be determined in part by day length 
and in part by night temperature (Mauney and 
Phillips, 1963), so that there is a seasonal 
flowering cycle. This regular cycle is missing in 
tomentosum. Mrs. Sinclair (1885:23) noted that 
it flowered the year round; and the herbarium 
specimens in the Bishop Museum were collected 
in every month of the year except December. 
During the present study it was found that in 
any population — at least from February through 
May-— most of the plants are vegetative and the 
remainder may have young flower buds, open 
flowers, or ripe bolls. Seeds can therefore be 
collected over a long period, but only from 
relatively few plants at any given time. 
Although tomentosum can be considered a 
dry-land plant, it appears to be less xerophytic 
than Caribbean hirsutum. Wild forms of the 
latter species will often thrive around salt ponds, 
and immediately exposed to strong winds and 
salt spray. Forms which grow in dry scrubland 
away from the coast tend to be components of 
more open vegetation, or else to grow tall. 
Typically they are not found as an understory 
among taller plants. In contrast, the most vig- 
