SUPPLEMENT n 



11. 33-4, for e.g. VESQUE . . . KOHL (1886), read (see BURGERSTEIN, 1904, 



P-I3) 



1. 51, after the cell-sap, read which then becomes more concentrated, for 

 But the cell -sap . . . retarding transpiration (P. 37, 1. 6) read Now one should 

 imagine that, owing to the osmotic energy of the cell-sap and the imbibition 

 energy of the membrane as well as of the plasma, the exposed surface of a 

 plant would, at least under similar conditions, give off less water vapour than 

 a water surface of the same extent. In practice, however, it has been found 

 that evaporation from expressed sap takes place at least as rapidly as from 

 pure water (WissER, 1904). Since, however, the surface of a plant actually 

 gives off usually far less water than a free water surface, there must exist 

 arrangements in the plant by means of which transpiration is retarded. One 

 of these, more especially, is the cuticle. 



37, 11. 7-8, for between varieties of cuticle read in behaviour of the external 

 wall of the epidermal cells 



1. 10, for gelatinous read non-suberised 



38, 1. 4, for Pneumachodes . . . 1896) read (comp. HABERLANDT, Phys. Anat.), 

 and -insert : As in the experiment above quoted, so also in nature, a movement 

 of gases can be detected taking place through the stomata when a difference 

 exists between the atmospheric pressure and the pressure in the intercellular 

 spaces. Such a difference may arise, e.g., by mechanical compression of these 

 spaces when the plant parts are bent through the agency of wind or animals, 

 or by chemical alteration of the intercellular gases in C0 2 -assimilation (Lecture 

 IX) and in respiration (Lecture XVI). In addition to such movements of gas 

 in bulk, gaseous diffusion also always plays an important part ; it is due to 

 unequal concentration of the gases in two different regions, and is quite analo- 

 gous to diffusion of dissolved bodies in a fluid medium. 



1. 27, after non-existent read (see Lecture X). Thus may be explained 

 the fact that under certain conditions transpiration from a leaf may almost 

 equal the evaporation from an equal surface of water (LIVINGSTON, 1906). 



I. 38, after tulipifera read or (in winter) of Cyclamen, 



II. 47-50, /OP Even assuming that . . . alterations in these read The amount 

 of transpiration taking place from any plant organ depends not only on the 

 structure of the cuticle and on the number and size of the stomata, but also, 

 and more especially, on its superficial extent and on its internal anatomy 

 (intercellular spaces). Even when all these structural factors are taken into 

 consideration still we are unable to estimate the total amount of transpira- 

 tion from an organ, since it is dependent in very large measure on external 

 conditions. 



39, 11. 14-35, for Dry soil hinders . . . guard cells of the stomata read Dry 

 soil retards transpiration very markedly. It has been supposed that this was 

 due to concentration of the cell-sap, or that the retardation of transpiration 

 was to be explained by the abundance of salts in the soil. As a matter of fact, 

 however, increased concentration of the cell-sap in the plant affects transpira- 

 tion only very slightly, and it has also been shown that frequently quite dilute 

 solutions have a marked influence on transpiration ; dilute acids retard, 

 dilute alkalis accelerate it. Hence the effect of soluble substances and of the 

 amount of water in the soil obviously cannot be purely physical, but, on the 

 other hand, complex, inasmuch as changes in the plant are first of all induced, 

 and these indirectly affect transpiration. Changes in the plant, however, 

 when at all rapid, are due to the activity of the stomata. 



11. 47-9, for Other plants . . . shows a stoma read Variations in the struc- 

 ture and mechanics of stomata are treated of in detail by HABERLANDT (Phys. 

 Anat.}. Fig. 8 shows a stoma 



