Since the Hawaiian Islands have never been connected to other land masses, the great
variety of plants in Hawaii must be a result of the long-distance dispersal of seeds, a
process that requires both a method of transport and an equivalence between the ecology of
the source area and that of the recipient area.
There is some dispute about the method of transport involved. Some biologists argue
that ocean and air currents are responsible for the transport of plant seeds to Hawaii. Yet
the results of flotation experiments and the low temperature of air currents cast doubt on
these hypotheses. More probable is bird transport, either externally, by accidental
attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent
excretion of the seeds. While it is likely that fewer varieties of plant seeds have reached
Hawaii externally than internally, more varieties are known to be adapted to external than to
internal transport. 【題組】50. What does the word excretion (line 10) mean?
(A)vomiting
(B)excursion
(C)exclusion
(D)emptying
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