142 USEFUL PLANTS OF GUAM. 
they are guided by the richness of the growth of bushes, which they 
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” (Vipha- 
grostis floridula), a few weedy labiates, and a sprinkling of ironwood 
trees (Casuarina equisctifolia). The boundary 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 sticky 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 entirely of coral 
gravel, This is excellent road material and the streets of Agafia 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 many 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 evreinalis, the nuts or seeds of which furnish the natives with 
food in times of famine; the wild fertile breadfruit (Artocarpus 
communis), having edible chestnut-like seeds; wild yams (J/oseorea 
spenosd), Which in places form impenetrable thickets: the betelnut 
palm (Areca cathecu), which is abundant in some of the rich valleys in 
