286 H. B, GUPPY, M.RB., 
certain one. The pods of another leguminous plant, Cana- 
valia obtusifolia, that climbs over the foliage of trees in North 
Keeling Island, also float on sea-water; but I do not know 
how long the beans will stand immersion, though judging 
from the wide dispersal of this plant, they probably will 
withstand it for a long period without injury. : 
The small cones of Casuarina equisetifolia, a tree that has 
been introduced intentionally into these islands, require a 
considerable amount of drying and exposure to the sun > 
before the seeds will germinate. Mr. Ross has found it 
necessary to bury them for some time, and then to expose 
them to the sun and rain before he could succeed in raising 
trees. This explains why none of the fallen and apparently 
well-dried cones that strew the ground under the trees ever 
germinate in that situation. Such cones will only float for 
one or two days in sea-water, a circumstance which shows 
that my experiment on the cones of Casuarina equisetifolia 
in the Solomon Islands (see Botany of the Challenger) was not 
earried far enough. Hence it is probable that they can only 
be transported by a drifting log or some similar agency. It 
is noteworthy, however, that although this tree is now 
spreading itself by natural means from island to island, it 
was not included, as far as we know, in the original flora of 
the group. 
Here end my observations on the flotation and mode of 
dispersal of the plants of this atoll. There are, however, 
some of the trees with the mode of dispersal of which I am 
not acquainted, as, for instance, Premna obtusifolia, found both 
on North Keeling Island and on the south coast of Java. 
Then agiain, how did the tiny seeds of Portulaca oleracea 
sticceed in reaching this atoll ? 
