Cæsalpinia Bonducella.—Old and New Worlds.
Scævola Kœnigii.—Usually regarded as confined to the Old World, but according to the synonymy accepted by some authors it is also to be ascribed to America. The genus is chiefly Australian, and it is possible that the littoral species may have reached America through the agency of birds, since all the species of the genus possess fruits that would attract frugivorous birds.
Ipomœa glaberrima (Boj.).—Old World.
Ipomœa pes capræ.—Old and New Worlds.
Vitex trifolia.—Old World. The genus is also dispersed by pigeons.
Cassytha filiformis.—Old and New Worlds. Like Scævola the genus is chiefly Australian, and here, also, the fruits of the littoral species are not only dispersed by the currents, but are known to be also disseminated by fruit-pigeons.
It is possible that birds may have taken a predominant part in the dispersal of the species of Scævola, Vitex and Cassytha.
There thus remain nine species for consideration. Of these two are exclusively American, three are found in both the Old and New Worlds and four are usually regarded as exclusively Old World plants, but one of them (Colubrina asiatica) has a fair claim to be regarded as of American origin. Thus it is quite possible that six out of these nine plants were brought to Hawaii from America through the agency of the currents.
NOTE 37 (page [78])
On Vivipary in the Fruits of Barringtonia racemosa and Carapa obovata
As observed by me in the Rewa delta, Fiji, there was no external evidence of such a process in the case of the fruits on the trees; but I did not pay very special attention to the matter, and it will be gathered from [Chapter XXX.] that the initial stage of germination may show no indication in the appearance of the fruit. More observation is needed for both species. As indicated in [Note 50], the structure of the seed of Barringtonia racemosa is suggestive of a lost viviparous habit. With regard to Carapa, Schimper (p. 43) remarks that he has never observed vivipary; but Miquel, in his Flora Indiæ Bataviæ, particularly speaks of the seeds germinating in the capsule. I think this is very likely, and that perhaps even the rupture of the capsule may be partly due to this cause.