MARSH AND SAVANNA VEGETATION. 57 



The fresh- water marshes are usually overgrown with reeds {Trichoon 

 roxburghii), associated with the great marsh fern {A crostichum aureum) 

 (PL IV), the climbing Lygodium scandens, and several coarse grasses 

 and sedges. The only trees are Pariti tiliaceum and a euphorbiaceous 

 tree called "alom," probably a species of Echinus. Growing about 

 the margins of swamps are the small Bacopa monniera, a creeping 

 scrophulariaceous plant with blue flowers and the habit of growth of 

 purslane; Ambuliaindica and A. fragrans, with an aromatic, camphor- 

 like odor; Centella asiatica, the Asiatic pennywort; Aeschynomene 

 indica; a species of Polygonum; and the water fern (Ceratopteris 

 gaudichaudii), which has edible fronds. Several large aroids occur 

 both cultivated and growing spontaneously, among them the common 

 taro {Caladium colocasia), the caulescent Alocasia indica, and Alocasia 

 macrorMza. The introduced abaka, or "Manila hemp" (JHusatextilis), 

 grows in several places, but it is not now cultivated by the natives. 

 At least two species of bamboo grow on the island, the most useful 

 and durable of which {Bambos blwneana) is armed with recurved 

 spines and forms impenetrable thickets in several places. 



SAVANNAS. 



These are grassy upland regions almost devoid of trees and shrubs. 

 They are characterized by a red clay -like soil and lack of drainage, 

 and by the reappearance of beach plants and marsh plants which are 

 absent from the forests. Xijiheagrostis floridula, which covers large 

 areas, is called " sword grass" by foreigners on account of the cutting- 

 scabrous edges of its leaves (PL LXIX). It grows higher than a man's 

 head and offers refuge for deer. Roofs thatched with this grass are 

 more durable than those of coconut or of nipa palm leaves, but more 

 work is necessary in their preparation and they are not common 

 except in regions where coconuts and nipa palms are scarce. Other 

 savanna plants are the bracken-like fern Gleichenia dichotoma (PL L), 

 Odontosoria retusa, Schizoloma ensifolium, Blechnum orientale, Pteris 

 biaurita, Lycopodiwn cernuum (PL V), (the wawae idle, or "rats- 

 foot" of the Hawaiians), and the little golden star grass Hypoxis 

 aurea. The only tree is the ironwood (Casuarina equisetifolia), which 

 also grows on the margin of the sea. Among other beach plants 

 which reappear here are the shrubs Lobelia koenigii, Pemphis acidida, 

 and Melastoma marianum; the composites Stemmodontia biflwa, 

 8. canescens, and the Bidens-like Glossogyne tenuifolia; also the 

 grasses Dimeria chloi'idiformis, Stenotaphrum subidatum, and Cento- 

 theca lappacea. The pretty little climbing marsh fern Lygodium 

 scandem is common, and the lavender-flowered morning glory Ipomoea 

 choisiana also occurs. 



