290 
J. ARTHUR HARRIS AND JOHN V. LAWRENCE 
sixth columns contain the actual differences between the mean values 
for the plants of the ruinate and of the three other habitats and of the 
region as a whole. These are obtained by subtracting the values for 
each of the habitats compared from the values for the ruinate as 
given in the second column. The same method is followed in drawing 
up the three other comparison tables to be discussed below. 
The signs of the differences are positive throughout. Thus the 
concentrations prevailing in the plants of the ruinate, which has been 
recognized by Shreve and others as the most xerophilous of the Blue 
Mountain habitats, are higher for both herbaceous and ligneous 
plants and for all species of plants than those in any other habitat. 
They are over two atmospheres higher than those found in the plants 
of the neighboring leeward ravines, over one atmosphere higher than 
those of the ridge forest and from over two to more than three atmos- 
pheres higher than those demonstrated on the windward side of 
the range. 
The relative values, obtained by dividing the mean concentration 
of the plants of the ruinate by those of each of the other habitats, 
show that the concentration of the sap of the plants of the most 
xerophytic of the habitats is from about 20 to 30 percent more con- 
centrated than that of the leeward ravines, about 10-13 percent more 
concentrated than that of the ridge forest, and from 30 to 35 percent 
more concentrated than that of the plants of the windward habitats. 
Table IV, giving the relationship between the sap properties of 
Table IV 
Growth Form 
Ridge Forest 
Ridge Forest Compared with Other Habitats 
Ruinate of 
Leeward Slopes 
Leeward 
Ravines 
Windward 
Slopes 
and Ravines 
All Habitats 
Herbaceous .... 
8.63 
-1. 14 
+ 1.04 
+ I.II 
-0.17 
1. 00 
0.88 
1. 14 
0.98 
11.54 
-I-5I 
+ 0.71 
• +1.81 
+ 0.10 
1. 00 
0.88 
1. 15 
1. 19 
I.OI 
All species 
II. 01 
— 1.06 
+ I.I2 
+2.05 
+0.42 
1. 00 
0.91 
I. II 
1.23 
1.04 
the plants of the ridge forest and those of the other habitats, shows 
that the plants of this habitat have a concentration lower than that 
of the comparable growth forms of the ruinate but higher than that 
of either the leeward ravines or the windward ravines and slopes. The 
amount of the difference is as great as 2 atmospheres in one case only. 
