74 PLANT PHYSIOLOGY. 



CORRELATED TOPICS. 



Theories of osmotic pressure. Plasmolysis. Isotonic coeffi- 

 cients. The micellar hypothesis of the structure of mem- 

 branes. 



Effects of temperature upon osmosis in roots, and the very 

 important ecological consequences. 



Mechanical value and use of turgescence. Tension of tissues, 

 and rigidity. 



Distribution and movement of air, minerals, and water in the 

 soil, and the resultant upon the structure, size, and form 

 of the root, and other parts. Mechanical analysis of soils. 



Physics of entrance of gases through stomata. Positive and 

 negative gas-pressure in plants. 



Physics of transfer from root-hairs to ducts. 



Absorption of water by green parts, and special structures; 

 and by seeds. 



Water-culture. 



Corrosive power of roots ; their ' ' selective power. ' 



LITERATURE. 



On Osmosis there are important notes in Nature, vols. 54, 55, 



and 58 (see index to those volumes). 

 Note by Leavitt in American Journal of Science, 7, 1899, 381, 



first part only. 

 Particularly see Brown, Vice-Presidential address in Nature, 



60, 474, 544. 



B. Transfer (a) of Water and Minerals. 



You have found that the water absorbed by root-hairs is 

 transferred to the ducts and given a good start up the stem. 

 It is now to be traced through the plant. 



33. What is the exact path of transfer of water through the 

 stems of plants? 



Answer by Experiment 16. 



EXPERIMENT 16. This may be tested by coloring the moving 

 water through use of a harmless dye in stems transparent enough to 



