142 USEFUL PLANTS OF GUAM. 



they are guided by the richness of the growth of bushes, which the}^ 

 are careful to burn upon the site. The leguminous shrubs undoubt- 

 edly act as nitrogen storers. Peanuts could be cultivated with advan- 

 tage for this purpose, and would be useful as a crop to alternate with 

 maize and tobacco. 



Savannas. — On the higher parts of the island there are stretches of 

 land almost bare or covered with sword grass, called "neti" (Xipha- 

 grostis Jloridula), a few weedy labiates, and a sprinkling of iron wood 

 trees {Casuarina equisetif olid). The boundar}^ between the savannas 

 and the wooded region is very sharply marked. All savannas are 

 characterized by absence of drainage. The soil is a red clay, which 

 becomes stick}^ and paint-like when wet, so that during the rainy season 

 the roads across the savannas in the southern portion of the island 

 become dangerously slippery and impassable. An analysis of savanna 

 soil showed it to be almost devoid of organic matter, free from gravel 

 and coarse sand, and consisting almost entirely of clay and silt. 

 Although it is rather low in nitrates it is possible that this deficiency 

 might be remedied by cultivation and the application of manure. 

 Though the amount of water-soluble phosphate contained by it is lower 

 than in the soils examined from other parts of the island, yet, accord- 

 ing to the report of the Bureau of Soils, it is as large as that in many 

 productive soils of the United States, and it is quite possible that some 

 savanna grass good for forage may be found to replace the coarse, 

 sharp-leaved neti, which is of little economic value except for thatching. 



Cascajo, or gravel. —The subsoil of the mesa and the cliffs forming 

 the sides of the plateau consist in many places almost entirety of coral 

 gravel. This is excellent road material and the streets of Agana are 

 formed of it. When first removed it is soft and crumbling, but it 

 becomes hard and compact on exposure to the air. It consists largely 

 of calcium carbonate. Similar material is used in the Philippines for 

 road building, but it does not stand heavy travel for a long time 

 and must be renewed at intervals. According to the report of the 

 Bureau of Soils, material of this kind gradually decomposes into a red 

 clay exceedingly high in iron compounds, and when organic material is 

 present frequently becomes converted into black waxy fertile soils 

 resembling, in man}- respects, the adobe soils of the southwestern 

 United States. 



INDIGENOUS AND SPONTANEOUS ECONOMIC PLANTS. 



Among the plants growing without cultivation on the island are 

 Cycas circinalis, the nuts or seeds of which furnish the natives with 

 food in times of famine; the wild fertile breadfruit {Artocarpus 

 communis), hewing edible chestnut-like seeds; wild yams (Dioscorea 

 spinosa), which in places form impenetrable thickets; the betel-nut 

 palm (Areca cathecu), which is abundant in some of the rich valleys in 



