OSMOTIC CONCENTRATION OF TISSUE FLUIDS 275 
determination may have been somewhat arbitrary, it was not in- 
fluenced in any measure by the magnitude of the constant, for the 
collections were all classified before the corrected freezing point lower- 
ings were calculated. Thus there seems no possibility of personal 
equation influencing the results. 
II. Presentation of Data 
I. Ruinate of Leeward Slopes 
The slopes which were once cleared for coffee or cinchona planting 
but have since been abandoned — in a large part, long ago — are known 
locally as ruinate. 
The ruinate is characterized, as is of course to be expected, by a 
relatively large number of introduced, in some cases widespread, 
species. 
While the ruinate has been described by writers as a xerophilous 
scrub formation, it occupies an area supplied with an abundance of 
precipitation, quite as much in fact as the primaeval forest of the 
same slopes. 
In so far as the conditions are really those of a xerophytic environ- 
ment they must be due to {a) edaphic conditions influencing water 
absorption, and {h) to the lowness and openness of the stand, per- 
mitting free air movements with consequent increased transpiration. 
The classification of this vegetation as xerophilous is due, we 
believe, to two factors. First, in contrast to the extreme hygrophily 
of the ravines of both leeward and windward slopes, the structurally 
really mesophytic species of the ruinate have a far more xerophytic 
aspect than they would if growing in a region of more moderate 
humidity, just as they would pass for decidedly mesophytic types in 
deserts like those of southern Arizona. Second, there are a number 
of truly desert species which have a profound effect upon the physiog- 
nomy of the vegetation. Agave is not common but Yucca aloifolia 
is frequently seen. Baccharis scoparia is probably the chief form 
lending a xerophytic aspect to the vegetation. 
What we have just said concerning the ruinate applies to only the 
areas in the neighborhood of 5,000 feet where our determinations were 
made. Below this level, and especially on the southern face of the 
Port Royal mountains, conditions are much drier and the truly desert 
species more numerous. 
