168 PLANTS, SEEDS, AND CURRENTS 



Nip a formation, a brackish- water swamp association predominantly 

 characterised by Nipa fruticans and stretching inland in the rear 

 of the coastal mangroves. But it is confined to the drier ground, 

 and herds with Cerbera odollam and some other characteristic beach 

 trees of the Barringtonia formation that are equally at home at the 

 beach margin and at the swamp border. In Jamaica I observed it 

 growing in the loamy soil behind the mangrove belt in the company 

 of several other plants, such as Coccoloba uvifera, Conocarpus erectus, 

 Guilandina bonducella, Hibiscus tiliaceus, and Thespesia populnea, 

 that are often associated with it at the margin of the beach. When, 

 as in Jamaica, it appears on the beach, it will usually be found also 

 occupying the low district in the rear. But its behaviour in Jamaica 

 supplies another clue. When one reflects that in the society of the 

 Mesquite (Prosopis juliflora), Cactacece, Yuccas, etc., it thrives in 

 the scrub of the extensive Liguanea plains in the interior (Harsh- 

 foerger, p. 678), the suspicion arises that Acacia farnesiana, being 

 primarily a xerophyte, only presents itself in this island as an intruder 

 on the beach. 



We obtain the same clue when we glance over the other parts of 

 the West Indies. Millspaugh found it growing inland on St. Thomas, 

 as well as on the seashore of Porto Rico, and also at Santiago de 

 Cuba (Plantce Utowance). In the case of Inagua, one of the Bahamas, 

 Harshberger found it associated with Opuntia and Phyllanthus in 

 the low thickets of the strand, and in the same company it came 

 under my notice in the interior of Grand Turk. As in Jamaica, 

 the chaparral formation, a more or less impenetrable scrub of Acacias 

 (including A. farnesiana), Prosopis juliflora, Cactacece, Yuccas, etc., 

 covers the arid plains of the interior of Hispaniola, an island in 

 which Willdenow was inclined to look for the home of the plant we 

 are now discussing. But it is not in the islands that the chaparral 

 is best developed, but on the mainland, as in the arid interior of 

 Mexico, Texas, and the Calif ornian Peninsula as described by Harsh- 

 berger. Here amidst a motley group of xerophytes, in which 

 Cactacece, Yuccas and Acacias are conspicuous, the plant we are 

 now concerned with is at home; and the ever-prevailing Mesquite 

 (Prosopis juliflora) is its frequent associate. When this scrub 

 descends from the elevated tablelands of Mexico to the plains that 

 border the Gulf and extend along the shores of Texas, Acacia farne- 

 siana accompanies it to the sea-coast. In such situations its claims 

 to be ranked as a strand plant would be no greater than those of 

 the numerous other xerophytes of the chaparral scrub that descend 

 with it to the coast. 



If the matter ended here there would be little difficulty in deciding 

 the point at issue. But not uncommonly in the West Indian region 

 and in other parts of the world Acacia farnesiana, as already remarked, 

 discards its associates of the chaparral and takes its place amongst 

 the characteristic littoral trees. Having explained how the plant 

 reaches the coast from the inland regions we have now to ascertain 

 why it remains there. In the answer to this question we may per- 

 haps find a key to its wide distribution over the globe. It associates 

 with quite different plants in the arid regions of America, Africa, 



