FRYER— FORMATION OF ALDABRA, ETC. 415 



genus Khizophora* is uniformly scattered through almost every part of the swamp and 

 also forms forests in one or two places, notably Picard and Camp Frigate, which 

 contain but few trees of other species. In habit it prefers a deep mud and an abundant 

 supply of water. The genus Bruguiera is represented by two species, B. gyrnnorhiza 

 and another not yet determined, which together form a large proportion of the forest 

 along Malabar and Main Islands and especially to the south of Michel Island. It is the 

 largest tree on Aldabra and reaches a height of 60 — 70 ft. When old, the trunk is 

 usually straight without any branches on the lower portions, and is consequently much 

 used for timber. 



Of the genus Ceriops there are apparently three species, C. Candolleana and two 

 others. On Aldabra it is an uncommon genus and is most prevalent at " Lance Cavallier," 

 south of Esprit Island, on Esprit itself, and on Main Island north-east of Michel. One 

 species, known in Creole as " manglier xerophe," forms a very straight trunk and is much 

 used for poles and posts. 



Both the last two genera do not require much mud, and are tolerant of a rocky 

 situation, and one which the tide reaches for but a short period. Khizophora and 

 Bruguiera are both cut for the bark, which contains a high percentage of tannin and forms 

 the chief export of the atoll. 



Of other mangrove-swamp trees there are five genera, the most prevalent being 

 Avicennia (A. officinalis) which is found all round the lagoon between tide marks, 

 especially in sandy places ; it also forms a large forest in the extreme east of the atoll, 

 where the trees attain a large size. 



Sonneratia acida, the second pseudo-mangrove, is decidedly scarce and occurs only 

 on Esprit and on Picard Islands. It is known as " manglier fleurs " for its large and 

 conspicuous flowers. 



Carapa obovata and moluccensis are both found on Esprit Island, and the latter on 

 Picard and on one of the islands in the western channels. At Esprit a small forest is 

 formed by C. moluccensis between the ridge of rock, previously described, and the true 

 mangrove swamp. 



A comparison with other mangrove swamps is difficult, as the writer has had little 

 further personal experience of them. It may however be mentioned that the Seychelles 

 swamps compared with those on Aldabra were scattered and the trees small, while the 

 latter, when compared with those further East, appear to be formed more entirely 

 of true mangroves and to contain less undergrowth, the palm (Nipa fruticans) being 

 absent. 



2. Pemphis Bush. This type of bush is composed almost entirely of Pemphis 

 aciclula and is found in conjunction with the metamorphosed limestone. The habit 

 of growth of the species has already been dealt with ; it may be mentioned in addition 

 that dead small branches do not always drop off but season in position, forming hard 

 skewer-like spikes. The wood is extremely hard and speedily turns the edge of an axe, 

 while it is hardly touched by insects, though occasionally a tree will be found to contain 

 a nest of large ants. 



* Khizopttora mucronata. 



53—2 



