48 MANGROVE SWAMPS 
employed in the manufacture of inner soles for shoes and can 
be used as a substitute for cork or pith. 
The small branches are more rounded than in Sonneratia alba. 
The leaves are thick and leathery, rounded at the apex, 6 to 10 
centimeters long, and nearly as wide as long. Two or three 
flower buds are usually found together. The calyx is green, 
leathery, 3 to 4 centimeters long, and divided into six to nine 
narrow segments, which are equal in length to the calyx tube 
or longer. The petals are white, narrow, and fall off very 
early; they are nearly as long as the calyx segments. Some- 
times there are no petals. The stamens are very numerous and 
the style long. The fruit is hard, rounded, depressed at the 
apex, 3 to 4 centimeters in diameter, and surrounded nearly 
to the middle by the calyx tube, the lobes of which are still 
present when the fruit is mature. The fruit contains many 
seeds. 
Family 9, RHIZOPHORACEAE 
The family Rhizophoraceae is the most important one in the 
mangrove swamps and contains by far the largest number of 
species. The members of this family in the swamps are dis- 
tinguished at once from all other species by the fact that the 
seed germinates and produces an elongated seedling before the 
fruit drops from the tree. This character is shown clearly in 
the illustrations of the members of this family. The conspicuous 
part of the seedling that projects from the fruit is the radicle 
or young root, which is very much longer than the plumule 
or young shoot. The family Rhizophoraceae is represented in 
the swamps by three genera; Rhizophora, Bruguiera, and Ceriops. 
Trees of the genus Rhizophora are easily distinguished from 
all other trees in the swamps by the very numerous prop roots 
which grow out from the trunk and branches. These are shown 
very clearly on Plate I. The genera Bruguiera and Ceriops can 
be separated by the shapes of the leaves, which in Bruguiera are 
pointed at the apex and in Ceriops are rounded and notched at 
the apex. 
Key to the genera. 
1. Leaves pointed at apex. 
2. Tip of leaves with prominent projection of midrib._.............. Rhizophora. 
2. Tip of leaves without projection of midrib.....................-..-....--- Bruguiera. 
1. Leaves rounded and notched at apex..............-----.-----------+--0sese-=--o= Ceriops. 
Genus BRUGUIERA 
The genus Bruguiera is represented in the Philippines by 
four species: Bruguiera conjugata (busain), B. cylindrica (poto- 
tan-lalaki), B. sexangula (potétan), and B. parviflora (lan- 
