Chap. VI] EDAPHIC INFLUENCES IN THE TROPICS 



403 



laeoides gradually shed their cortex. 

 Avicennia officinalis (Figs. 223, 4 ; 

 224), together with the two American 

 species, Sonneratia acida and S. 

 alba, Ceriops Candolleana, and the 

 American combretaceous Laguncu- 

 laria racemosa, all have negatively 

 geotropic lateral roots protruding 

 from the ground like asparagus ; 

 these are as long as one's finger, 

 or, in Sonneratia, one's arm. The 

 species of Rhizophora do not 

 possess special pneumatophores.yet 

 the upper parts of their stilt-roots 

 that are above the mud perform 

 the same function. 



That pneumatophores supply 

 subterranean parts of the trees upon 

 which they occur with oxygen was 

 proved by G. Karsten and Greshoff. 

 as has been already explained 1 . All 

 these structures are accordingly 



provided with devices for absorbing 



oxygen (lenticels, sto- 



mata, thin cork) and 



for transporting it (in- 

 tercellular passages in 



the primary cortex or 



bast). 



By means of a sketch 



written on the spot, I 



have attempted in the 



following paragraphs 



to give a description 



of the physiognomy 



of the mangrove in 



Java : — 



' The lagoon-like bay 

 in South Java known 

 as the "Kindersee" is 

 separated on the south 

 from the Indian Ocean 



Fig. 224. Avicennia officinalis. Pneumatophores. 

 Mangrove, Java. Half natural size. 



Fig. 225. Brugniera gymnorrhiza with knee-roots. Mangrove, low 

 tide, South Liu-kiu. From a photograph by O. Warburg. 



1 See p. 73. 



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