HYDROHARMOSE 



III 



repotted in a loose sandy soil often enougii. This permits the root system 

 to develop normally, and also makes it possible to wash the soil away with- 

 out injury to the root. The method is so recent that there has been 

 no opportunity to test it in the field. It would seem that it can be applied 

 without essential change to plants in their normal habitats. Very large 

 herbs or plants with extensive root system.s could not be used to advantage, 

 and to be practicable the experiments would need to be carried on near the 

 base station. The great value of the method, however, lies in its use as a 

 check in determining the accuracy of other methods, and in practice it will 



Fig. 31. Absorption and transpiration of Helianthus annuus. I and 

 II, plants repotted in soil of known weight and water-content; III, 

 plant undistured in the original soil; IV, potometer containing plant 

 with cut stem; V, potometer with entire plant. 



often be found convenient and time-saving to use the latter, 'after they have 

 once been carefully checked for different groups of species. This matter is 

 further considered under measures of transpiration. 



156. The quantitative relation of absorption and transpiration. 6ur- 



gerstein^ has summarized the results of various investigators in the state- 

 ment "that between the quantitative absorption of water on the one hand 

 and emission on the other there exists no constant parallelism or proportion," 



^ Die Transpiration der Pflanzen, 14. 1904. 



