TROnCAL MARINE MARSHES 241 



rubber tree, or Indian fig, which is a familiar object in green- 

 liouses. The branches, however, have a widespreading, rather 

 low habit, and from them as well as from the crown of the tree 

 there ^rrow off long, runner-like processes which extend for a 

 distance of some feet in a horizontal direction, and then curving 

 sharply downward descend through the water until they attain 

 the bottom, where they take root. These curious processes, 

 though at first slender, gradually increase in size and become 

 strong supports, from which new crowns, with their trunks and 

 branches, may spring. Thus a single tree may rapidly march 

 away from the original planting-point until its outer verge may 

 be an indefinite distance from its place of origin. 



Underneath the close-set crowns of the mangrove the 

 roots make a dense tangle, where a host of marine animals har- 

 bor and contribute their dlhris, in the way of sediments, 

 to the bottom. At the same time the tidal waters, having 

 their current arrested by the obstructions which they encoun- 

 ter in the submarine part of the forest, deposit quantities of 

 mud. These accumulations, mingled with the leaves and 

 branches which fall from above, serve rapidly to shoal the 

 water until marshes take the place of fields which were before 

 inundated even at low tide. When this state in the growth 

 of a mangrove plantation is attained, the species which have 

 won their way against the sea gradually die out and their 

 place is taken by others which, though they can not live in 

 contact with salt water, can flourish on the marshy accumula- 

 tion formed by their predecessors. 



Owing to the vigor of growth of the mangrove trees and 



to the peculiar roots which they put forth, they can withstand 



the assaults of much heavier waves than the frailer marsh plants 



of higher latitudes. The mangroves of southeastern Florida 

 16 



