248 



In order to insure a sufficient supply of oxygen for the rootd, 

 many trees in these forests are supplied with so-called pneumato- 

 phores, or aerating roots. In some species these grow up from 

 the ground and look like thick shoots of asparagus, in others 

 the roots bend up out of the ground and form knee-like struc- 

 tures, while in some -cases the upper surface of the roots 

 alone projects above the ground. These serial roots, or portions 

 of roots, are usually covered with thin cork and possess abundant 

 lenticels. " The mode of propagation is most remarkable in 

 Rhizophora mucronata, which in this respect agrees in the main 

 with the other Rhizophoraceae living in the mangroves. The fruit 

 leathery and indehiscent and about the size of a hazel-nut, 

 soon after the completion of its growth is pierced at its summit 

 by the green hypocotyl, as the embryo does not undergo any 

 period of rest, but continues to develop without interruption. 

 The hypocotyl in R. mucronata is club-shaped and attains a 

 length of 60 centimetres, sometimes even more, before it falls 

 down, leaving behind it the fused cotyledons which served as 

 absorbing organs. As its lower end is thicker, the seedling falls 

 vertically, with its root-tip downwards into the mud, and within 

 a few hours develops roots that fix it firmly."* 



The principal genera in these forests are 



Rhizophora. Carapa. 



Ceriops. Avicennia. 



Kandelia. Sonneratia. 



Bruguiera. Lumnitzera. 



Among shrubs Acanthus ilicifolius (with leaves like holly 

 and blue flowers) and Mqiceras are common. 



The two small palms Nipa trulicans and Phoenix paludosa 

 form gregarious thickets in the Sundarbans and littoral forests 

 of Burma. Common climbers are species of Denis ; epiphytes 

 are scarce and there are usually no mosses. Ferns and grasses 

 often form the undergrowth in the drier spots. 



Further inland above high-tide mark, on ground which is 

 only occasionally, if ever, flooded, the following are 

 characteristic : 



Hentif.ra Fomes. The Sundri, which is the most important 

 tree in the Sundarbans. 



Thespesia populnea. 

 Hibiscus iiliaceus. 



* Schimpor op. cit., pp. 396398. 



