54 



out the available soil, so that little is left to support a heavier 

 vegetation. 



Practically the whole southern slope may be roughly divided 

 into these three areas, the first, of course, being much the largest. 

 And all these are in a great measure controlled by the presence 

 or absence of available surface water. It is, in short, to this eda- 

 phic factor that we must turn for an explanation of the barrenness 

 of the slopes, the profusion of the canons, and the sterility of the 

 river bottoms. With soil, light, and climatic conditions so even 

 throughout this great southern exposure, there is only this insta- 

 bility and inequality of terrestrial water sources that can account 

 for the marked diversities existing among these three types. 



It is unnecessary to discuss the strand and littoral, as they are 

 much the same throughout the West Indies and have little to 

 do with the problem of the general or regional distribution of the 

 plants of this area. 



Turning now to the windward or northern slope and the ridge 

 of the Maestra, we have entirely different conditions prevailing. 

 Here the northeastern trade-wind keeps the country continually 

 bathed in great quantities of moisture, and the precipitation is 

 heavy. From this constant equality of moisture supply and an 

 almost similar equality of temperature this ridge is an ideal envi- 

 ronment for moisture-loving plants of all kinds. 



The vegetation forcibly reminds one of the lowland canons, 

 but it is much more dense ; so much more so that without cut- 

 ting a path it is impossible to scramble through. Many plants 

 occur here that we had never seen at the lower elevations, but 

 the number of species is so great and the time spent here so 

 short, that any list based on the present collections would give 

 no adequate idea of the richness and variety of the flora. Filmy- 

 ferns, tree-ferns, epiphytic orchids and bromeliads, hepatics and 

 mosses, together with many Peperomias, seem to predominate, 

 but the whole effect is one of bewildering complexity and density. 

 The vegetation is evenly distributed at all the points that we 

 visited on the ridge and windward slope, but the line of demarca- 

 tion in this belt is clearly seen when one begins the descent to 

 the sea, thus leaving the region that comes under the influence 

 of the trade-wind. 



