654 
plants is higher than 4°.4 C., yet it is not probable that the plants of 
the lowlands are excluded from the top because of low temperature 
alone. 
The topography.—The topography is such as to offer no very stable 
place for vegetation to gain a foothold. It consists of the knife-like 
ridges, which seem to be characteristic of tropical, voleanic mountains 
in a youthful stage of erosion, and precipitous slopes leading to the 
principal streams which lie at the bottom of the canons separating 
these slopes. The latter, in turn, are cut up into ‘steep ridges and side 
cafons, the inclination of both of which in places may be very 
precipitous. The side cafons such as are found near the headwaters 
of the Lamao River, during the rainy season, present waterfalls and 
cascades, and the side ridges usually end in the precipitous walls of 
the Lamao River canyon. (Pls. I and. IL.) 
In contrast with the topography of lower altitudes, that of the top of 
the mountain presents narrower main ridges and steeper side ridges 
and canyons. 
The ridge vegetation —LKight plots were made, each one corresponding 
to a definite physiographic outline on the main south ridge leading 
from a peak ridge at 900 meters’ altitude to Buena Vista peak (altitude 
1,266 meters) on the rim of the crater, a distance of about 6 kilometers. 
These plots were undertaken with the purpose of determining the nature 
of the vegetation in this situation and of discovering, if possible, what 
factors, climatic and edaphic, determine the differences. 
Description of Table XXII. 
A is a plot approximately 8 by 45 meters at 900 meters extending through an 
altitudinal range of 3 to 4 meters. It is an exposed peak, with soil composed 
of clay, some loose rock, and a half-disintegrated outcrop of voleanice rock. B is 
a plot 6 by 37.5 meters at 900 meters’ altitude on top of a hard, voleanic rock 
with little soil. It is an exposed peak. C is a plot 5 by 30 meters at 914 
meters’ altitude on a level ridge, not as exposed as A or B. The soil is a heavy 
clay, with some loose rock, although it presents no outerop. Plot D is irregular 
in shape, comprising about 175 square meters on an exposed cliff which shows 
a voleanic outerop of rock, with a little shallow soil in places (altitude 1,034 
meters). Plot E has an area of 7 by 45 meters on a level stretch, at 1,034 meters 
in altitude. The soil is composed of deep clay, with large bowlders which have 
withstood weathering processes. F is a plot of 4 by 48 meters, on a bluff similar 
to that of Plot D, but with slightly more soil (altitude 1,100 meters). G is a 
plot of 4 by 50 meters at an altitude of 1,135 meters on a level ridge which 
has a fair amount.of clay soil, although’ semidisintegrated rock is near the sur- 
face. Plot H with an area of 5 by 35 meters is at an altitude of 1,265 meters 
(Buena Vista peak). The soil characteristics are similar to these encountered 
in Plot A, but the exposure is greater. I is the total of each species in all plots; 
J, the percentage of each species in all plots. No trees under 3 meters are 
included and none reached a height of over 15 meters. 
