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APPENDIX 



often predominates in the interior with shrubs like Tournefortia 

 gnaphalodes on its weather border, and beyond them, reaching to 

 the wash-line of the sea, Euphorbia buxifolia, Cakile fusiformis, 

 Sesuvium portulacastrum, Ipomcea pes-caprce, etc. 



In those cases where the original sand-keys lie close together and 

 are only separated by shallow channels the mangroves lead to their 

 ultimate union. Cases are cited in this paper where two keys, 

 separated at the time the islets were charted by the U.S. Hydro- 

 graphic Survey, were found by Mr. Lansing to be joined together. 

 Writing of the Marquesas Group of these Florida sand-keys, Dr. 

 Millspaugh says that through the growth of the mangroves and the 

 upwashing of the light coral sand by the waves all the keys will in 

 course of time unite to form a solid island embracing the whole 

 group. It is, however, instructive to note that this growth of islands, 

 whether singly or in combination, takes place under the conditions 

 of the present sea-level. We get no indication in this paper of the 

 formation of the seolian sandstone which has so long puzzled the 

 geologist both in the Bermudas and in the Bahamas. The con- 

 ditions for its development are not presented in the history of these 

 Florida sand-keys. 



With reference to the means of dispersal through which these 

 keys received their plants, Dr. Millspaugh holds that the balance is 

 on the side of the bird, and he appeals mainly to the medium of the 

 feet of sea-birds. However, I have endeavoured to adjust our views 

 in the remarks made below on the probable mode of dispersal of the 

 nineteen plants he names as most typical of these keys, to which I 

 have added four which deserve a place in this treatment of the 

 subject of dispersal, namely, Ipomcea tuba (= Calonyction album), 

 Ipomoea pes-caprce, Canavalia obtusifolia, and Sccevola plumieri. A 

 grouping of the plants according to their probable mode of reaching 

 the Florida sand-keys is here presented. For particulars reference 

 should be made to other pages of this work, to my book on Plant 

 Dispersal, to my paper on Keeling Atoll, and to Dr. Millspaugh' s 

 paper. 



(A) Plants brought by the currents, the seeds, fruits, seedlings, etc., 

 being able to float long enough to reach these sand-keys : Avicennia 

 nitida, Batis maritima, Cakile fusiformis, Canavalia obtusifolia, 

 Conocarpus erectus, Ipomcea pes-caprce, Ipomoea tuba, Laguncularia 

 racemosa, Bhizophora mangle, Salicornia ambigua, Suriana maritima, 

 Tournefortia gnaphalodes. 



(B) Plants brought by currents and frugivorous birds : Sccevola 

 plumieri. 



(C) Plants brought through the adherence of their fruits to birds' 

 plumage : Cenchrus tribuloides, Euphorbia buxifolia (Millspaugh's 

 authority). 



(D) Plants with small seed-like fruits that possess sufficient float- 

 ing power to enable them to be brought by currents from neighbour- 

 ing coasts, but which could also have been transported in the crevices 

 of drifting logs : Ambrosia crithmifolia, Borrichia arborescens. 



(E) Plants with small seeds or seed-like fruits, all non-buoyant, 



