xxx RHIZOPHORA 



447 



(3) It is not easy to explain the gregarious growth of the Selala 

 if it is a seedless hybrid. The colonies could not be renovated 

 by mere intercrossing, especially in places where, as on the north 

 coast of Vanua Levu, the dense belt of mangrove is for many miles 

 composed in mass of Selala trees, with a few trees of the Asiatic 

 and American Rhizophoras growing on the outskirts. 



It is obvious that in order to clear the way for considering this 

 problem the means of renovating the Selala colonies should be 

 inquired into. In the first place, whilst seedlings occur in numbers 

 under the trees of the other two Rhizophoras they are never to be 

 found under the Selala trees. The mode of reproduction of the 

 Selala is evidently vegetative, and the question arises as to what 

 mode of vegetative reproduction occurs. The Selala trunks, as 

 already observed, are often inclined, the trunks being supported on 

 trestle-like aerial roots. These trunks send out branches which in 

 their turn drop aerial roots ; and when the decay of the parent 

 trunk takes place, the branches are able to live independently. The 

 primary branches in due time send out secondary branches which 

 also let fall aerial roots ; and thus the process is repeated in- 

 definitely, the result being a maze of semi-prone trunks, branches, 

 and aerial roots. The first stage of the process ends with the death 

 of the parent trunk, and the primary branch, supported by its own 

 aerial roots, is often all that the observer can distinguish in the 

 centre of a colony. This is evidently the mode by which the Selala 

 colonies are renovated in their interior. One sometimes observes 

 in the midst of one of these colonies extensive bare mud-flats 100 

 to 500 yards across from which apparently the trees have died off 

 en masse. The natives assert that when part of a Selala tract is 

 cleared the trees never grow again. 



But pari passu with this process of vegetative reproduction of 

 the Selala, by which the mass of the colony is preserved and 

 renovated, there is evidently some other process of reproduction in 

 operation amongst the trees of Rhizophora mangle and R. 

 mucronata at the edge of the colony, as a result of which Selala 

 seedlings are produced. Whilst no seedlings are to be observed 

 striking into the mud under the Selala trees, numbers occur, as 

 before observed, under the trees of the other two species. Those 

 under the trees of R. mangle possess in nearly all the cases the 

 distinctive leaf-characters of that mangrove, and would be recog- 

 nised at once as belonging to that species. On the other hand, 

 those beneath the trees of R. mucronata are of two kinds, some of 

 them being readily recognised by their foliage as of the Selala type 



