142 UvSKKUL PLANTS OK OFAM. 



tlicv arc nuitUMl by the liclincss of the growth of l»u«hcf^, which thev 

 arc caicfiil to Iturii mxni the site. The leji'uminouis .shrubs undoiiht- 

 edly act as nitrt)oeu i^torers. Peanuts could bo cultivated with advaii- 

 ta<>c for this puipose, and would be useful as a crop to alternate with 

 maize and tobacco. 



Savannas. — On the hio-her parts of the Island there arc stretches of 

 land almost bare or covered with sword g-rass, called "ncti" {XipJm- 

 (/rodisjhtrldula), a few weedy labiates, and a sprinkling of ironwood 

 trees {Cmi(at'h)a ef/nisc'tlfolia). The ])()undary between the savannas 

 and the wooded region is very shar})ly marked. All savannas are 

 characterized b}- absence of drainage. The soil is a red clay, which 

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

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

 ])ecome dangerously slippery and impassable. An anal3\sis 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 a|)plication 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 possi))le 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 entirel}' 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 largel}^ 

 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 

 resem])ling, 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 

 Gycas circinalis^ the nuts or seeds of which furnish the natives with 

 food in times of famine; the wild fertile breadfruit (Artoca?'j)us 

 eohimnnis)^ having edible chestnut-like seeds; wild yams {Dtoi^eorra 

 sj>nios((), which in places form imp«>netrable thickets; the ))etel-nut 

 palm {A/'eca cathccti), which is abundant in .some of the rich valleys in 



