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 



■>>»>'>un^MidlM>«lW«Mi<W«iA<«l 



i j Kiiim jumliMm 



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

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

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

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

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



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

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

 lormal structure : (i) Reduction of surface, the volume being assumed 



