450 
J. ARTHUR HARRIS AND JOHN V. LAWRENCE 
481. Palicouria alpina 
Phthirusa parvifolia . . 
Dendrophthora gracilis 
484. Vaccinium meridionale. . , . 
Phthirusa parvifolia . . 
Dendrophthora gracilis 
A = o. 
A = I. 
A = I. 
A = I. 
A = I. 
A = I. 
.83, P = lo.o 
.23, P = 14.8 
.12, P = 13.5 
.32, P = 15.9 
.39. P = 16.7 
.34, P = 19.I 
In all, the osmotic pressure of the juices of each of the two or three 
parasites is higher than that of the host, although they may differ 
sensibly between themselves. 
One of the most interesting cases is that of a broad-leaved loranth, 
Phthirusa parvifolia parasitic upon a leafless member of the same 
family, Dendrophthora gracilis which is in turn parasitic upon a tree of 
Cyrilla racemiflora about twenty feet in height (Coll. 196). 
The sap properties stand in the following relationship. 
Cyrilla racemiflora A = 1,18, P = 14.2 
Dendrophthora gracilis A = 1.26, P = 15.2 
(on Cyrilla racemiflora) 
Phthirusa parvifolia A = 1.49, P = 17.9 
(on Dendrophthora gracilis) 
Osmotic pressure increases from host to the primary parasite and 
from the primary parasite to the secondary one. 
Note also that the observed secondary parasitism is Phthirusa 
parvifolia with an average depression of 1.35° upon Dendrophthora 
gracilis with an average depression of 1.18°. 
Whether the reciprocal case of secondary parasitization ever occurs 
could only be determined by more extensive field observation. 
The demonstration of the lower osmotic pressure of the tissue 
fluids of the leafless as compared with the leafy species of Loranthaceae 
requires no special discussion at the present time. The validity of 
this conclusion, based primarily upon averages, although also evident 
in the general trend of the individual constants, is evidenced for by 
certain favorable combinations of parasitism. 
In four cases (Col. 204, 247, 481, 484) it was possible to secure 
determinations from a leafless and a leafy form upon the same host. 
As shown by the table above, the osmotic pressure of the leaves is 
higher in each case than that of the stems of the associated leafless 
parasite. 
IV. Discussion of Results 
