XXVI DODON^A 339 



with the first-named, and his hesitation to include it as one of the 

 innumerable forms of the widely-ranging D. viscosa is very sugges- 

 tive. However, whether or not one or both of these peculiar forms 

 are connected in their origin with this species, it is certain that the 

 genus has been established for ages in Hawaii ; and from D. viscosa 

 we can learn how a species of the genus can cross an ocean, and 

 also how from a widely-ranging species exhibiting extreme varia- 

 bility species peculiar to a group of islands could have been 

 derived. 



The great variability of Dodonsea viscosa is associated with 

 great adaptability to different stations. Thus, as Mr. Hemsley 

 tersely puts it, it is one of those plants that thrive on the sea-coast 

 as well as inland, and in almost any soil or situation — provided, it 

 may be added, that the station is well exposed to the sun. Although 

 Mr. Ridley characterises it as a regular sea-shore plant in the Malay 

 peninsula, and although Prof Schimper places it in the Indo- 

 Malayan strand-flora, it is as an inland plant that it is most charac- 

 teristic of the Pacific islands ; and the key to its powers of adapta- 

 tion to different stations is to be found in its xerophilous habit. 

 It is essentially a plant of sunny places, and is equally at home on 

 the parched inland plain, in the open wood, on the sandy beach, 

 on an old lava-field, or on rocky declivities. It is not a plant of 

 the rain-forest, preferring dryness to humidity and sunshine to 

 shade. 



The following remarks on the mode of dispersal of the wide- 

 ranging Dodonaea viscosa will serve to roughly indicate the 

 capacity of the genus for distribution. It is a subject, however, 

 that requires further detailed investigation. The light, inflated, 

 winged capsules of this species, about an inch across, could be 

 blown for long distances along the ground and carried for short 

 distances in the air by strong winds, but, as is also remarked by 

 Prof Schimper {Ind. Mai. Strand-flora, p. 157), they are much too 

 large to be transported by winds across a broad tract of sea. The 

 currents, however, may have aided in the dispersal of the species 

 in the case of island-groups 500 or 600 miles apart. Although the 

 membranous capsules before dehiscing would be unable to with- 

 stand the " rough-and-tumble " of ocean-transport for more than a 

 few days, the seeds possess some floating powers of a purely acci- 

 dental nature due to the imperfect filling up of the seed-cavity in 

 some of the seeds. In an experiment made in Hawaii I found 

 that only half the seeds floated in sea-water. Prof Schimper, in an 

 experiment conducted in Germany with seeds that must have been 



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