44 THE AMERICAN BOTANIST 



swamps throughout the tropics. This extraordinary combina- 

 tion of structural and ecologic characters — vivipary, aerial 

 roots, ability to grow in salt water, rapid lateral growth and 

 freedom from fungus and insect pests — has given to the man- 

 groves a tremendous advantage in the invasion of tropical 

 coasts. 



The name mangrove is derived, by corruption, from the 

 original Malayan name niangi-mangi. The American species, 

 R. mangle L., is called Red mangrove, referring to the color 

 of the inner bark. There are various trees in (3ther regions 

 that are called mangrove, that are not true mangroves and do 

 not belong to the mangrove family. The white "mangrove" 

 is Lagiincularia racemosa of tropical America. The l)lack 

 mangrove is Avicemiia nitida; also of tropical America and 

 sometimes called olive mangrove. The mangrove mvrtle is 

 Barringtonia aciitaiigiita of the East Indies. The milkv man- 

 grove is Bxcaccaria agallochuni of Australia. The Tasman- 

 ian "mangrove" is Acacia longifolia. The river mangrove is 

 Aegiceras majiis of Indo-Malaya and Australia. 



The American mangrove, which is the species represented 

 in the Hawaiian Islands, is abundant along the coasts of 

 Florida, tropical America, the West Indies and the Galapagos 

 Islands. It forms vast monotonous green thickets and is the 

 van of advancing vegetation along the salt marshes. Its maze 

 of roots make it an effective land builder and it rapidly gives 

 a footh(jld to less hardy species. In West Indian waters, for 

 example, mangrove islands are formed so rapidly that in a few 

 years they dot the shallow waters of bays which were formerly 

 destitute of them. 



The tree is round-topped, bushy and usually 15 — 20 feet 

 high. Its branches are spreading, like those of the hau and 

 its roots make almost impenetra])]e tliickets. Sometimes, in 

 inland situations, the tree grows erect, attaining a height of 



