30 MANGROVE SWAMPS 
Key to the genera of mangrove-swamp plants. 
[Based on superficial characters. ] 
1. Palms. 
2. Stemless, with underground rhizomes; without spines.. Nipa, page 26 
2. Trunks erect with numerous, long, slender spines.. Oncosperma, page 30 
1.A large coarse fern with pinnate leaves rising in a cluster from the 
betes 25 ok oor ot tal eee pee oe oes Acrostichum, page 26 
1. Not palms or ferns. 
2. Leaves pinnate with one to three pairs of leaflets. Large trees with 
round fruit 8 to 25 centimeters in diameter and containing a few, 
‘wery slaree, angular (seeds. 12 3 so .58 Xylocarpus, page 30 
2. Leaves not pinnate; fruits not as above. 
3. Leaves opposite. 
4. Herbs or shrubs with spiny-margined leaves.... Acanthus, page 76 
4, Leaves not spiny. 
5. Leaves usually pointed at the tip. 
6. Tip of leaf with prominent projection of the midrib. 
Rhizophora, page 56 
6. Tip of leaf without projection of the midrib. 
7. Petioles usually not over 2 or 3 millimeters in length. 
Sonneratia, page 38 
7. Petioles usually more than 6 millimeters in length. 
8. Lower surface of leaves green; with long, slender seedling 
projecting from the fruit... Bruguwiera, page 42 
8. Lower surface of leaves gray or white; fruit a capsule 
up to 2.5 centimeters in length and containing a single 
SCG Creer. Be ae Ae ee ee Avicennia, page 74 
5. Leaves rounded at apex and not notched; mature leaves usually 
more than 3 centimeters in breadth. 
6. Petioles usually more than 1.5 centimeters long; flowers 
about 1 centimeter in length... Scyphiphora, page 78 
6. Petioles usually much less than 1.5 centimeters in length; 
flowers about 5 centimeters long... Sonneratia, page 38 
5. Some or all of the leaves slightly or conspicuously notched at 
apex. 
6. Petioles very short, much less than 5 millimeters in length. 
Osbornia, page 66 
6. Petioles more than 1 centimeter in length... Ceriops, page 54 
3. Leaves alternate. 
4. Small shrubs; leaves with toothed margin........ Pluchea, page 78 
4. Margin of leaves smooth or nearly so. 
5. Tips of leaves usually pointed, or lower surfaces of leaves with 
a silvery appearance. 
6. Petioles more than 2 centimeters in length; plants with 
abundant milky juice. 
7. Leaves more than 15 centimeters long; flowers large, white, 
CErMIn a) 22-2 k eee eee ee ee ee Cerbera, page 70 
7. Leaves less than 12 centimeters and usually less than 10 
centimeters long; flowers very small, from branches below 
ChE ICAV ES! 22s: eee ee ST See nee, Excoecaria, page 34 
6. Petioles less than 2 centimeters in length; plants without 
milky juice. 
7. Leaves rounded at the base...................... Heritiera, page 36 
7. Leaves pointed at the base.................... Brownlowia, page 34 
