APPENDIX 



451 



Different stages in the process are readily distinguished. It 

 begins with the partial emergence of a bank of coral sand, which 

 under the influence of the currents gradually acquires a more or less 

 curved or crescentic form, its convexity facing the currents. For 

 convenience we will take a medium-sized key and will designate the 

 convex side of the bank as its weather margin. Whilst the bank is 

 still washed over by the seas in places, various floating seeds and 

 fruits, as well as seedlings, are cast up on its surface, those of the 

 mangroves, more particularly the seedlings of Rhizophora mangle, 

 establishing themselves under the shelter of the bank on its lee side. 

 Islets may remain in the condition of a mangrove colony for some 

 time. But as the exposed surface increases in extent typical beach 

 plants begin to establish themselves. The seeds of some are brought 

 by sea-fowl; but, as will be shown later on, the currents probably 

 do most of the work. One of the first to establish themselves on the 

 bank on the weather side is Sesuvium portulacastrum, and it is this 

 plant that Dr. Millspaugh places at the head of his list illustrating 

 the sequence of appearance of the most characteristic beach plants 

 on these keys. This is followed in the order fixed by this authority 

 by Cakile fusiformis, Euphorbia buccifolia, Cenchrus tribuloides, 

 Cyperus brunneus, JJniola paniculata, Andropogon glomeratus, 

 Suriana maritima, Tournefortia gnaphalodes, Borrichia arborescens, 

 Iva imbricata, and Ambrosia hispida (A. crithmifolia). 



Two strand plants not sufficiently frequent on these keys to be 

 included in the most representative plants, but amongst the first to 

 establish themselves through the aid of the currents, not only on 

 West Indian beaches, but also on new islets in the Indian and Pacific 

 Oceans, are Canavalia obtusifolia and Ipomcea pes-capraz. Their 

 place in the above list would be with the plants immediately following 

 Sesuvium portulacastrum. Another of the early plants would be 

 Sccevola plumieri, though it only grows on a few of the keys. 



By the time that the sandy surface is well stocked with beach 

 plants the mangrove colony on the concave side of the bank has 

 increased extensively, and we notice that though in great mass of 

 Rhizophora mangle, two other mangroves, namely, Avicennia nitida 

 and Laguncularia racemosa, have established themselves on the 

 border facing the sandbank, where they are associated with Cono- 

 carpus erectus. The mud-flat in the neutral zone between the beach 

 plants and the mangroves is ultimately occupied by Salicornia 

 ambigua, Balis maritima, and Sesuvium portulacastrum. 



We now approach the completed stage in the history of such a 

 key, a condition which it is likely to preserve, provided man does 

 not intervene, as long as the present relation between land and 

 water prevails. Be the islet small or large, a limit to its growth at 

 the borders is reached in the deeper water, both on the weather side, 

 where the waves cease to heap up the sand, and on the lee side, 

 where the Rhizophora colony no longer extends seaward. Through 

 the reclaiming agency of the mangrove, the area of the swamp is 

 much reduced and the beach plants advance on the new surface. 

 The islet loses its crescentic form, and in the final stage it is mainly 

 appropriated by the beach plants, amongst which Suriana maritima 



