Journal of Agricultural Research 
Vol. VII, No. s 
258 
The freezing points of the expressed juice of apples, sweet potatoes, 
potatoes, and strawberries were determined by means of a Beckman 
freezing-point apparatus, and the total diffusion tension for the material 
in these solutions was calculated from the lowering of the freezing 
point (15). 
The results obtained by the calculation of these data are given in 
Table II. 
Table) II. —Diffusion tension in atmospheres of the juice of certain hosts of the fungi 
studied , as calculated from the lowering of the freezing point 
Host. 
Diffusion 
tension | 
(atmospheres.) 
Strawberry. 
8. 27 
17 * 85 
10. 25 
6. 52 
Apple (Blacktwig). 
Sweet potato (Jersey Big Stem). 
Potato (Irish Cobbler). 
From Table I it is evident that the fungi used in these experiments 
are able to grow in relatively high concentrations of salts and sugars. 
The highest diffusion tension of any solution in which growth was 
evident was in the concentrated solutions of glucose. Growth occurred 
in all concentrations of this sugar used. 
With potassium nitrate growth was inhibited in all cases when the 
diffusion tension of the solution was about 59 atmospheres; and in only 
one case was a fungus able to grow in a solution so concentrated. All 
the fungi except the two strains of Rhizopus nigricans and Glomerella 
cingulata grew in concentrations which have a calculated diffusion ten¬ 
sion of 47 atmospheres. 
The fungi also grew in solutions of sucrose of rather high concentra¬ 
tions, the two strains of Rhizopus nigricans and Diplodia tuhericola being 
the only fungi which were unable to grow in sucrose solutions having a 
diffusion tension of 40 atmospheres. It is noticeable that growth in the 
case of R, nigricans is inhibited also at lower concentrations of potassium 
and calcium nitrates than with the other fungi. 
Calcium nitrate inhibited germination and growth always at concen¬ 
trations considerably lower than those required to produce the same 
effect with sucrose, glucose, and potassium nitrate. Nevertheless a 
comparison of the diffusion tensions of the highest concentrations of 
calcium-nitrate solutions in which the fungi grew and the diffusion ten¬ 
sion of the juice of the host plant as calculated from the lowering of the 
freezing points shows that the parasite is in all cases able to grow in 
considerably higher concentrations than are present in the cell sap of 
its host plant. Whether or not the protoplasm of the fungi used is 
impermeable to the two salts and two sugars used in these experiments 
