OSMOTIC PRESSURE OF TISSUE FLUIDS 
449 
been included a considerable amount of juice from woody tissue not 
at all comparable with the leaves of the host.^^ 
Note too that while the juices of D. opuntioides gave a freezing 
point lowering of 0.360° less than that of the old leaves of Oreopanax, 
they gave a depression slightly greater than that of young Oreopanax 
leaves from the same tree, e., A ~ 1. 165 as compared with A = 1.144. 
The older leaves of Oreopanax gave a juice which was too gelatinous to 
filter. Whether or not this has influenced the accuracy of the deter- 
mination of the freezing point of the host leaves we cannot assert. 
There remains but one further exception, Phthirusa paucifolia on 
Citharexylum caudatuni. At first sight the A of the host seems suspic- 
iously high, but the three other determinations for this species made on 
trees from which parasites were not secured give A = 1-772, A = 1.945, 
A = 2.048 with an average for the four of A = 1.950. There can, 
therefore, be no legitimate assumption that the constant for the host 
is too high. There seems, indeed, no valid objection to this exception 
to the rule of a higher osmotic pressure of the juices of the parasite. 
In its bearing upon the problem of the relative osmotic pressure 
of the solutions in the tissues of the two organisms the following cases 
of two or more species of parasites occurring on the same host plant 
are of great interest.^^ 
The cases are arranged by the hosts. 
204. Baccharis scoparia 
A = 1. 15, P = 13.8 
A = 1.42, P = 17. 1 
Dendrophthora cupressoides 
A = 1. 19, P = 14.4 
A = 1.28, P = 15.4 
A = 1.50, P = 18.0 
Dendrophthora cupressoides 
A = 1.26, P = 15. 1 
A = 1. 41, P = 16.9 
A = 1.63, P = 19.6 
Phthirusa paucifolia 
A = 1. 71, P = 20.5 
A = 1.59, P = 19. 1 
292. Duraniia repens 
A = 1.29, P = 15.5 
A = 1.40, P = 16.8 
Phthirusa lepidobotrys 
A = 1.39, P = 16.7 
^" This is also true of D. cupressoides on Baccharis discussed in a preceding 
paragraph. 
^4 In collecting samples of this kind it was often impossible to secure ample 
materials of both of the parasites from the same shrub or tree. In such cases great 
care was taken to obtain materials of both parasites from the same individual trees 
and to compound the sample of the host plant from these trees in order to avoid all 
possibility of having the comparability of the samples jeopardized. 
