Floristik, Geographie, Horticultur etc. 379 



The floras ot" Islands in the Pacific are first considered tVom 

 the Standpoint of dispersal by currents. The floating capacity of 

 seeds and fruits has been tested in a number of plants, and statistics 

 of the duration of buoyancy are given. It is cstimated that about 

 10 p.cent, of the indigenous species of the Fijian group of islands 

 are found on the coast, and the seeds or seed-vessels of almost all 

 these float for some da3's, while three-fourths continue to float for 

 two months or more. Two other large groups of Pacific islands — 

 the Hawaiian and the Tahitian — are similarly analysed. So far 

 as Pacific islands are concerned, the author assumes two princi- 

 ples: (a) "that the plants with buoyant seeds or seed-vessels have 

 been for the most part located at the coast"; (b) "that in a genus 

 comprising both coast and inland species, only the coast species 

 possess buoyant seeds or seed-vessels". 



''The Lesson of the British Flora" (Chaps. III and IV) has been 

 learned from an examination of the floating capacity of about 300 

 British species of seeds and fruits. The proportion of British flowering 

 plants with buoyant seeds or seed-vessels is much lower than in the 

 case of Pacific islands, but the majority are plants found either 

 on the sea-coast or on the margin of strcams and lakes. The investi- 

 gation shows that only about one-third of the British coast-plants have 

 seeds capable of prolonged buoyancy, hence dispersal by ocean cur- 

 rents cannot be regarded as an important factor. Similarly, only a 

 limited number of plants occurring on the margin of fresh-water are 

 dispersed by buoyant seeds. The explanation offered is; "It is the 

 fitness or unfitness of a plant for living in dry situations that pri- 

 marily determines the Station. If a xerophilous plant has a buoyant 

 seed or seed-vessel it finds its way ultimately to the coast; if it is 

 hygrophilous and its seeds or fruits can lloat, then it is finally 

 established on the side of a pond or river". 



Comparing the strand-floras of the three great groups of Pacific 

 islands which have as their centres Fiji, Tahiti, and Hawaii 

 respectively, the Fijian is shown to be the most complete; they can 

 be arranged into plants of the mangrove-swamp , plants of the sandy 

 beach, and plants ol the intermediate districts. The plants of the 

 beach formation extend inland, because they have "the xerophilous 

 Organisation", and the plains and other scantily vegetated areas offer 

 a Station. The true mangroves are absent in the Tahitian and 

 Hawaiian islands and with them many plant-associates although 

 the majority of the mangrove plants have seeds or fruits capable oi 

 prolonged buoyanc}-. The Hawaiian group has a meagre littoral 

 flora, but this "cannot be attributed to lack of suitable stations, or 

 to climatic conditions or to delicicnt floating power of the seed or 

 fruit". Consideration of the currents of the Pacific naturally foUows, 

 and it appears that the Indo-Malaj^an plants have extended east- 

 ward to the Tahitian islands against the stream of the South 

 Equatorial Current, except from Januar}^ to March when the 

 Northwest Monsoon prevails. It is shown that the currents of the 

 Pacific have failed to establish the beach-trees of the Pacific islands 

 not only in the Hawaiian group, but also on the coast of America; 

 an American origin for the shore-plants of Hawaii is supported. 



"The results of Observation and experiments are given to show 

 that there is no direct relation between the specific weight of seeds 

 and fruits and the density of sea-water". Schimper's view that the 

 buoyancy of many seeds and fruits may be claimed as adaptations 

 is contested, and "it is urged that buo3'ancy is connected with 



