404 ZONES AND REGIONS [Pt. Ill, Sect. I 



by the hilly island of Noesa-Kambangan, but otherwise enclosed by the shores of 

 the main island, here quite flat. Several rivers pour their sluggish waters into 

 it, and, as they lie low, they feel the influence of the tides even at a great dis- 

 tance from their mouths. Most of them subdivide into several arms. The deltas 

 they enclose are under water at high tide, but a little above water-level at low tide. 

 A better substratum for the development of mangrove could hardly exist, and 

 it is accordingly developed with rare luxuriance. 



' When travelling in a canoe along the banks of the creek, or along one of the 

 numerous arms of the rivers, one does not always observe the same landscape. 

 On exposed shelving coasts, Rhizophora mucronata is almost alone capable of 

 resisting the violence of the waves or of propagating itself in the troubled water ; 

 but here on these flat shores, where breakers are unknown, the conditions of 

 existence are far more nearly equally favourable to the various species of plants, 

 so that sometimes one, at other times another, species gains the victory in the 

 struggle for space. Sometimes the shore is occupied by a dense belt of Rhizo- 

 phorae; sometimes one passes by a little forest of silver-grey, willow-like Avicennia 

 officinalis, var. alba ; at still other points the dull green foliage of Sonneratia acida 

 predominates, or the outposts are held by a narrow hedge of Nipa fruticans. Here 

 and there occurs the remarkable spectacle of a Carapa obovata, whose brownish- 

 yellow ,'fruits, as large as one's head, peep from the small crown of the tree, or 

 one sees a bush of Aegiceras majus covered with snow-white flowers and curved 

 horn-shaped fruits. The two species of Bruguiera (B. gymnorrhiza and B. parvi- 

 folia) that grow here are less frequent on the margin of the mangrove in contrast 

 with their abundance in its interior, where the crowns of B. gymnorrhiza tower 

 above the other trees, whilst the much smaller B. parviflora with inconspicuous 

 blossom is less noticeable. 



' At low tide one can see the confused crowd of the stilt-roots of Rhizophora, 

 or the crop of asparagus-like rootlets of Avicennia and Sonneratia, with their 

 population of fishes and crabs. I have nowhere else seen the knee-roots of Bruguiera 

 gymnorrhiza in such numbers and dimensions. At other points the sharply keeled 

 roots of Carapa obovata creep with manifold bends over the surface of the mud. 



'At high tide the whole complex of roots is invisible; even the lowest leaves of 

 Rhizophora and of Sonneratia remain for some time submerged. From my 

 canoe I could see young plants of Rhizophora mucronata in the deep water. 



' Epiphytes are very scarce in the mangrove, and at its outer edge are entirely 

 wanting on Rhizophora mucronata. Apparently the salty surface does not suit 

 them, as it renders the substratum, that is already poor in water, still drier 

 physiologically. Only in long creeks and in the interior of extensive mangroves, 

 where the wind does not blow salt spray on to the branches, do epiphytic species, 

 like Platycerium grande and P. alcicorne, also on the " Kindersee " Hydnophytum 

 montanum, become more numerous. Small lichens however always occur, but no 

 mosses ; mosses are very halophobous plants.' 



An account of the Algae that cover the roots of the trees will be given in the 

 chapter on aquatic plants (p. 791). 



In tropical East Asia and Australia, lagoons more distant from the sea, 

 where however the soil is still subject to tidal influence, but is less saline, 



