696 PROCEEDINGS OF THE ACADEMY OF [Oct. 



ulata, Caiderpa mexicana, C. racemosa uvifera, Ulva laduca, etc. The 

 sandy bottoms beneath mangrove trees or in the channels leading 

 from salt water sounds or ponds to the sea are characterized by 

 Halimeda tridens, Penicillus capitatus, Caulerpa taxifolia, C. cupressoides 

 lycopodium, Padina pavonia. The salt-water ponds, especially at 

 Walsingham, are fed by underground channels, so that the water in 

 them rises and falls with the tide. Here grow several interesting 

 marine algae, such as Valonia utricularis, Caulerpa plumaris, C. 

 racemosa, and Colpomenia sinuosa. 



Mangrove Swamp Formation. 



The mangrove swamps occur at the heads of bays, especially along 

 the south shore of the Bermudas and in the salt-water ponds which 

 are here and there found distributed over the islands. The vegetation 

 consists either of a pure growth of Rhizophora mangle with its prop 

 roots extending in all directions, or a pure growth of Avicennia niiida 

 (in flower in June) with its numerous pencil-like root knees projecting 

 through the sticky mud at low tide. In some places, as in Castle Har- 

 bor, both Avicennia nitida and Rhizophora mangle are in association, 

 and frequently one finds arising from the mud the green brush-like 

 tops of Penicillus capitatus. Little else grows beneath the dense 

 shade formed by the overarching crowns of these trees. Frequently a 

 morass is formed by either Rhizophora or Avicennia taking possession 

 of a shallow inland pond which thus becomes a swamp. Several such 

 swamps are found near the coast on the north shore of Bermuda where 

 Avicennia nitida has taken possession and has excluded everything 

 else, except Pluchea purpurascens, Sesuvium portulacastrum, Salicornia 

 fruticosa, Heliotropium curassavicum and a low sedge. In the salt- 

 water pools in such swamps at Shelly Bay is found Ulva lactuca, and 

 on the projecting roots of Avicennia nitida a moss-like growth of con- 

 siderable bushiness. 



Salt Marsh Formation. 



This is found at the head of bays and elsewhere where the soil is in- 

 fluenced by the tides. In such a marsh along Harrington Sound the 

 writer noted Salicornia jruticosa, Heliotropium curassavicum, Sesuvium 

 portulacastrum and a number of sedges. The projecting roots from a 

 single tree of Avicennia were also observed together with the long up- 

 right culms of a form of the crabgrass, Stenotaphrum americanum. 

 The rare Statice Lefroyi also is a salt marsh plant. 



