Notwithstanding the considerable period of time over which these collections were made, and the possibility that some of the more extreme values may be due to some undetected error of determination, the range of osmotic pressure is actually rather narrow; though, when considered in comparison with the mean pressure, it is relatively rather wide. Expressing the results in the more logical terms of standard deviation, we find:

Experiment
C
D

E

Wall

0.304±0.039
0.211 ± 0.029
0.510 ± 0.057

Prolification

0.363±0.046
0.180±0.025
0.488 ± 0.055

The collections from Series E, which were made over a wide range of time and conditions, are distinctly more variable. This conclusion, based on the standard deviation, is substantiated by the determination of the coefficients of variation.

With regard to the relative conditions in the wall and the included mass, the results of this measurement of the concentration of non-electrolytes, and dissociated and non-dissociated electrolytes, are in close agreement with those for electrolytes alone, as measured in terms of conductivity. There is a lower osmotic pressure in the sap of the included mass than in the ovary wall. The great majority of these differences are of sufficient magnitude to be certainly significant. The data here are very consistent. Only three exceptions are found: in two the prolification has a greater osmotic pressure than has the sap from the ovary wall; in one the results are identical.

Turning to the summary giving the mean osmotic pressure for wall and abnormal tissue, and their differences, we note that the osmotic pressure of the sap of the included mass is from one half to one atmosphere lower than that of the wall of the fruit in which it is produced. Expressing the difference in percentages, as in the case of conductivity above and using as a base the mean for the ovary wall, we find that the osmotic pressure is 12.1, 7.0 and 6.5 percent lower in the mass. These relative values are distinctly

These three cases occur in one of the two small series. No explanation can be given.

lower than those for electrolytes, which were 34.7, 34.6 and 29.6 percent.

These facts seem to indicate that the differentiation between fruit wall and included mass due to electrolytes tends to be strongly reduced by the non-electrolytes. We noted that the difference for specific gravity was only from 5.50-11.50 percent, as compared with 30.00-35.00 percent for electrolytes. This may be taken as evidence in the same direction as the findings for osmotic pressure.

D. RATIO OF ELECTRICAL CONDUCTIVITY TO DEPRESSION OF THE FREEZING POINT. (Data, Tables 7-11.) We have desired to determine the amounts of mineral salts and organic constituents of the sap, but because of the great technical difficulties have been unable to do so for a series of materials as extensive as those with which we have had to deal. We have therefore contented ourselves with the determination of the ratio of the conductivity to the depression of the freezing point. While these are not measures in the same terms, a comparison of the ratios in such closely related materials as the tissues of the ovary wall and of the abnormal mass is perhaps quite legitimate.

This ratio is given in our tables as */Δ. On the assumption that nearly all of the electrical conductivity is due to dissociated inorganic salts, such a ratio shows the relative proportion of salts in the total solutes. The results are remarkably consistent. In only one sample does the difference between the ratios possess a positive sign. Thus the organic substances form a greater and the inorganic a smaller proportion of the solutes in the sap of the prolification than do those in the sap of the ovary wall. The averages for the three larger series are given below:

The constants for comparable tissues are in good general agreement from series to series, but the differences though actually very

TABLES 17-21

Data pertaining to concentration and mean molecular weights of solutes in

Thus, the

small are several times as large as their probable errors. difference between the ratio for exp. C and D is 0.000364±0.000036, that between C and E is 0.000245±0.000040, that between D and E is 0.000119±0.000048. The mean difference between the constants for the ovary wall and the included mass is in all cases over ten times as large as its probable error, and so unquestionably significant.

E. MEAN MOLECULAR WEIGHT OF THE SOLUTES IN THE SAP. (Data, Tables 17-21.) The results for mean molecular weight of the solutes is much less consistent from sample to sample than any other measure here discussed. This is to be expected from the technical difficulties in its determination. As we have computed

TABLES 17-21 (continued)

Data pertaining to concentration and mean molecular weights of solutes in

the saps

it, three laboratory operations are involved: (a) the determination of specific gravity by weighing in a pycnometer; (b) the determination of total solids by drying a pipetted sample (10 c.c.) at 100°; and (c) the measurement of the depression of the freezing point. A slight error in any of these processes would influence the final constant. Even in work with isolated chemical substances the determination of exact molecular weights by cryoscopic methods presents difficulties. The close agreement in the observed mean molecular weights is, we believe, a good criterion of the care with which our analyses have been carried out.

The ranges in mean molecular weight of the solutes for the several experiments are:

The differences in the ranges are quite striking. For both ovary wall and abnormal carpellary mass, exp. C and D show a far narrower range of variation than the other three series, notwithstanding the fact that exp. A and B, which show on the whole the widest ranges, comprise but a few determinations.10

For the three large series the standard deviations and coefficients of variation are:

Thus, the variation in the mean molecular weight in exp. E, as measured by the standard deviation or coefficient of variation, is distinctly higher than that of the two other large series, just as it appeared to be when measured by the range of variation. The explanation of this greater variability in certain of the collections is probably the same as that suggested for the observed differences in other constants-that of environmental heterogeneity and of differences in the physiological state of the individual at the time the samples were taken.