Chap. 1] 



WATER 



dryness, salinity of the substratum, illumination. Attention has been 

 chiefly directed to the leaves, as being the chief organs of transpiration. 



All experiments have led to essentially similar results. External con- 

 ditions which, either by diminishing the absorption of water or by 



4mmi^fi.i.u»^»»,nM«NM«>N 



6. 



Fig. i. Influence of transpiration on the differentiation of the leaf-tissne. Transverse sections 

 of leaves and stomata. i and 2. Lactuca Scariola : 1 exposed to sunlight, 2 grown in shade. 

 o.s. upper surface, a.s. under surface. 3 and 4. Robinia Pseud-acacia : 3 in ordinary air, 4 in air saturated 

 with vapour. 5-8. Sonneratia acida : 5 on wet saline soil, 6 on ordinary soil in the Buitenzorg 

 garden, 7 on saline soil, 8 on ordinary soil. 1-2 after Stahl, 3-4 after Lothelier, 5-S from nature. 



accelerating its exit from the plant, disturb the equilibrium in a sense 

 hostile to the plant, occasion, as a rule, the following deviations from 

 normal structure : (1) Reduction of surface, the volume being assumed 



