400 



ZONES AND REGIONS 



[Pt. Ill, Sect. I 





Fig. 213 numerous young plants of Rhizophora mucronata, in various 

 stages of development, are visible in a shallow pool, evidently of quite 

 recent origin, on the shore. In other Rhizophoraceae belonging to the 

 mano-rove the seedlings are smaller than in R. mucronata and not always 

 markedly club-shaped (Figs. 218 and 219). 



Vivipary is also exhibited by Aegiceras majus and Avicennia officinalis. 



The seedlings of Aegi- 

 ceras are curved like horns, 

 and are smaller than those 

 of the Rhizophoraceae ; 

 the)' remain enclosed in 

 the thin pericarp of the 

 fruit. Those of Avicennia 

 which fall, sometimes sur- 

 rounded by the leathery 

 pericarp that dehisces sub- 

 sequently, and at other 

 times without it, are pro- 

 vided with a bent and 

 densely hairy hypocotyl 

 and with two large cotyle- 

 dons. The hairs are stiff 

 and curved upwards, and 

 fix the seedling to the mud. 

 In the remaining man- 

 gro\e-plants vi\ipary does 

 not occur ; but the seed- 

 lings of some species, in 

 particular those of Acan- 

 thus ilicifolius and, in 

 America, of Laguncularia 

 racemosa, are always 

 further developed than is 

 usual in inland plants. 

 On proceeding more into the interior of the mangrove we find that other 

 woody species join Rhizophora mucronata and become dominant with 

 increasing distance from the sea. Bruguiera gymnorrhiza surpasses all 

 other mangrove-trees in size (Fig. 220). Other species of Bruguiera, 

 Rhizophora conjugata, Ceriops Candolleana arid Kandelia Rheedii, are 

 smaller trees or shrubs. Sonneratia acida (Fig. 221), which often forms 

 pure mangrove, is likewise a small tree ; the allied and similar Sonneratia 

 alba prefers stony ground, and frequently grows by itself in open situations, 

 outside the true mangrove. Avicennia officinalis also frequently forms 



Fig. 220. Bruguiera gymnorrhiza. J.ivanese mangrove. From 

 a photograph by G. Karsten. 





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