274 J- ARTHUR HARRIS AND JOHN V. LAWRENCE 
to US more important than a consideration of the primaeval forest of 
the leeward slopes. As the other extreme in the vegetation of the 
southern side of the ridge, the vegetation of the leeward ravine seemed 
desirable. 
In dealing with the collections from the windward sides of the 
mountains we have not found it practicable to follow the treatment 
accorded them by Shreve who discusses the ravines and the slopes 
separately. The two habitats blend quite imperceptibly into each 
other. The distinction between the vegetation of the two has seemed 
to us to be primarily one of the loftiness of the trees and the abundance 
of the extremely hygrophilous ferns, mosses, and hepatics. While an 
investigation of the concentration of the sap in the bryophytes and 
filmy ferns that are so characteristic a feature of the more hygrophytic 
habitats would be of great interest, we preferred to devote our time 
to the study of arborescent and herbaceous seed plants of the type 
to be met with in other regions with which comparisons are to be drawn. 
For this reason we have treated the collections from the leeward 
ravines and leeward slopes together. 
Our collections have, therefore, been distributed among the follow- 
ing habitats. 
I. Ruinate of the Leeward Slopes. 
II. Leeward Ravines. 
III. Ridges. 
IV. Windward Slopes and Ravines. 
The distinction between these habitats is by no means always 
sharply marked. Ravines and ridges are merely the extremes of the 
topographic series. Between them and the intervening slopes there 
is, from the purely topographical side, no sharp line of demarcation. 
Furthermore, the habitat distinctions are not based primarily 
upon the substratum but upon meteorological conditions. Air move- 
ments undoubtedly play a considerable role in determining the char- 
acter of the vegetation. Thus fog is often blown over the main ridge, 
rolling down the leeward slopes for some distance, to be dissipated 
below. The vegetation of the ridges which are at the same time gaps 
exhibits many of the characteristics of the ravine. 
In view of these facts it is altogether improbable that any two 
botanists would agree exactly upon the classification into habitats 
of a series of 398 collections — the number upon which the present 
discussion is based. While in some cases our disposition of a given 
