Osmotic Concentration and Electrical Conductivity, Etc. 137 



bility of K and of A cannot be asserted to be significantly 

 different in herbaceous species. 



Turning to the question of the relative variability of the 

 physico-chemical constants in the different growth forms we 

 note that the variability of the freezing point lowering of 

 trees is numerically greater than that of shrubs as measured 

 by both standard deviation and coefficient of variation. The 

 difference in the variability of the two groups of ligneous forms 

 is not, however, sufficiently large to be considered significant 

 in comparison with its probable error. The standard devia 

 tion of A in herbaceous forms is lower than that in either 

 trees or shrubs. The average osmotic concentrations, as 

 measured by A, is also lower in these forms. In consequence 

 the relative variability as measured by the coefficient of varia 

 tion is higher in herbaceous species. 



The variability from species to species of the electrical 

 conductivity does not differ, as far as the data now available 

 show, in the two groups of ligneous plants. The standard 

 deviations of the conductivities of herbaceous plants are 

 higher than those of ligneous species, but since the average 

 conductivities are also higher, their relative variabilities as 

 measured by the coefficient of variation are somewhat lower. 



Finally, the results of the ratio K/ A show that the standard 

 deviations are far higher in herbaceous than in ligneous plants. 

 The mean value of the ratio is also far higher, and as a result 

 the coefficients of variation of ligneous species are higher. 



Taking the results for variability as a whole, they seem 

 to indicate that there is little difference between ligneous and 

 herbaceous forms. 



The foregoing results show clearly that the osmotic con 

 centration is higher while the electrical conductivity is lower 

 in the tissue fluids of ligneous than in those of herbaceous 

 species. 



The results for freezing point lowering are drawn from 

 three climatically highly dissimilar regions. While those 

 for electrical conductivity are based on determinations from 

 one region only, they represent two years work. 



