308 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
efforts has possibly limited somewhat the precision of the deter- 
minations.* 
While I hope later to secure larger, and better, series of data 
on osmotic concentration in the tissue fluids of desert Loran- 
thaceae, and to obtain series from mesophytic regions for com- 
parison with those from the hygrophytic and xerophytic habitats 
now available, there is little prospect of the completion of this 
work in the near future. It seems proper, therefore, to place on 
record the results so far obtained on the desert species for the 
use of other physiologists. 
In the present state of our knowledge, determinations of the 
properties of the tissue fluids of desert Loranthaceae have a two- 
fold interest. 
I. In studies in the Arizonaf and the Jamaican coastal 
deserts, my associates and I have confirmed the conclusions of : 
Drabble and Drabble and of Fitting by showing that the osmotic 
concentration of the sap of desert plants is in general far higher 
than that of those of mesophytic and hygrophytic regions. It 
seems a matter of considerable interest to determine whether the 
same relationship holds for the Loranthaceae of these climatically 
antithetical regions. 
2. In our first study we found that the concentration of the 
tissue fluids of the parasite is generally, but not invariably, 
higher than that of the host plant. It seems desirable to test this 
* Because of the rapid evaporation in the Sever air, the danger of differential 
series. e 
necessarily subjected until they could be placed in the freezing mixture, the danger 
of es in the composition of the sap were necessarily greater than in the cool 
climate of the Blue Mountains. The concentrations in molecules and ions of the 
solutes, not the nature of the constituent compounds which may possibly be some- 
Aerei, is the subject under investigation. It may be doubted whether 
ven for a much longer time would өй alter concentration. Further- 
more, any дужа of this kind would be quite as likely to affect the tissues of both 
and parasite, and hence to leave the relationship between them unaltered, as to 
influence one alone. 
Harris, J. Arthur, & Lawrence, John V., with t óperation of Gortner, К. A. 
The cryoscopic constants of expressed vegetable saps as related to хойтын hae 
mental conditions in the Arizona deserts. Phys. Res. 2: 1-49. 1916. 
+ Harris, J. Arthur, & Lawrence, John V. Сгуоѕсоріс determinations on tissue 
fluids of plants of Jamaican coastal deserts. Bot. Gaz. 64: 285-305. 1017 
