(b) Mangrove-formation.—Carapa obovata, Rhizophora mucronata, Rhizophora mangle, Bruguiera Rheedii, Lumnitzera coccinea, Scirpodendron costatum, &c. (See below.)
(c) Intermediate or Transition-formation.—Hibiscus tiliaceus, Heritiera littoralis, Smythea pacifica, Derris uliginosa, Entada scandens, Barringtonia racemosa, Cerbera Odollam, Clerodendron inerme, Vitex trifolia, Excæcaria Agallocha, &c.
N.B.—It is not possible to draw a definite line between the plants of the mangrove swamp and those of the tracts around. Several of the plants placed in the intermediate formation, such as Heritiera littoralis, Entada scandens, Excæcaria Agallocha, &c., are just as much at home amongst the mangroves. In the same way it is often difficult to distinguish between the Beach and the Intermediate formations, and plants like Cerbera Odollam, Hibiscus tiliaceus, and Vitex trifolia belong equally to both.
NOTE 25 (page [47])
The Strand-flora of the Tahitian Region
Drake del Castillo’s Flore de la Polynésie française deals mainly with the Society or Tahitian Islands, but also with the Marquesas, Paumotus, Gambier Islands, and Wallis Island. The last-named, however, lies in Western Polynesia, and is not dealt with in this connection. There is no reason to believe, judging from the general character of the islands and from Cheeseman’s memoir on the Rarotongan flora, that the strand-plants of the islands of the Cook and Austral Groups, which also belong to this region, differ materially from those of the Tahitian islands proper. Rarotonga, however, possesses Entada scandens, not recorded as a growing plant from any other part of East Polynesia, excepting perhaps Mangaia in the same group.
NOTE 26 (page [48])
The Fijian Shore-plants not found in Tahiti
Although most of these plants, such as Barringtonia racemosa, Clerodendron inerme, Entada scandens, Excæcaria Agallocha, Heritiera littoralis, Smythea pacifica, &c., have fruits that float for months, and could have reached Tahiti as readily as some of the beach-plants that have successfully established themselves, there are a few like Dalbergia monosperma, Derris uliginosa, and Scirpodendron costatum, the fruits of which only float for weeks, and it is possible that they may have been unable to reach there.
NOTE 27 (page [49])
The Intruders into the Beach-flora from the Inland Plants of Tahiti
Drake del Castillo mentions several, such as species of Boerhaavia, that could only be occasional intruders; but it is noteworthy that Gardenia tahitensis appears to be a genuine recruit from inland. The xerophilous habit of the Pacific Gardenias and their station, usually near the coast, however, would render this possible.