SAMO SS ye 
384 
in certain salts, and, what is more important ecologically, its incapac- 
ity to hold water, and which supports the famous “eng” (Dipter- 
ocarpus tuberculatus) forests in that region. The soils of Mount 
Mariveles are not deficient in essential mineral salts and they show a 
very high capacity for retaining water. ests made of representative . 
specimens of the soil show that its average capacity to hold moisture is 
53 per cent in weight of water, calculated on the total volume of air-dry 
soil. It is very probable that this power has a great deal to do with its 
capability of maintaining a sufficiently high chresard during the dry 
season, during which time the underground water level is lowered and 
the supply of water brought by capillarity to the surface layers is 
consequently less. 
There is no serious contention that the chemical constitutents of soil 
has any pronounced effect on ecological distribution, for the reason that 
nearly all soils contain the essential elements in sufficient quantities.” 
Exception must be made to the deleterious nature of strongly alkaline 
and salty soils, and even here the effect is physical rather than chemical. 
In undisturbed conditions, with the exception of the amount tempo- 
rarily stored up in new growth, practically all which is taken from the 
soil by plants as mineral salts, is returned thereto in the shape of fallen 
leaves, twigs, etc.; it is only in cultivated ones where the crop is removed 
that they become worn out.*! Attention will be called to peculiarities of 
the soil under the heading of formations. 
THE PLANT FORMATIONS. 
The types of vegetation on the Lamao Reserve may be divided into six 
formations; viz, the Strand, the Bambusa-Parkia, the Anisoptera-Strom- 
bosia, the Dipterocarpus-Sh orea, the Shorea-Plectronia, and the Hugenia- 
Vaccinium. (See map.) 
TI. Tue BAMBUSA-PARKIA FORMATION. 
Character of the formation.—The vegetation at the base of the moun- 
tain has been given the name Bambusa-Parkia because it is believed that 
in the genera Bambusa and Parkia are exhibited forms of plants which 
best indicate the response in the vegetation to the ecological conditions 
which are obtained in the habitat in which these genera prevail. The 
response is such as to meet the almost xerophytic conditions present 
during the dry season. The genus Bambusa, represented by several 
species, has some of the ecological advantages of trees and many of those 
” For a review of the literature on this subject sco Cowles, H. C. The Influence 
of Underlying Rocks on the Character of the Vegetation. Bull. Am. Bureau 
Geography (1901). 
* See Livingston, B. E., Britton, J. C., and Reid, F. R. Studies on the Prop- 
erties of an Unproductive Soil. U. 8. Dept. Ag., Bureau of Soils Bull. (1905) 
28. In this paper it is maintained that “worn-out” soils may be poisoned ones. 
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