igoo-i.J Effects of Water on Foliage Leaves. 319 



amount of inorganic alkaline salts is extracted from leaves by the 

 application of pure water to the leaf surfaces. This may in some cases 

 prove of advantage to the plant, but it also might under certain 

 circumstances prove a decided disadvantage resulting from the too great 

 loss of useful mineral nutrient substances. 



Regarding the absorption by leaves of iron in solution, it is eas)- to 

 speak with certainty ; for, if one secure a plant, chlorotic (from lack of 

 iron in the culture medium), but otherwise in good condition, and place 

 a few drops of a dilute solution of Ferric chloride (m/640) carefully upon 

 a leaf, in twenty-four hours after^vards a green circular area is seen 

 where the drop was applied. Thunbergia alata was the only plant upon 

 which a sufficient chlorosis was obtained to demonstrate clearly this 

 phenomenon. The green area spread over the whole leaf in three days 

 to such an extent that the deep green of the leaf was uniform. Plants 

 chlorotic from starvation, as were some of those referred to in the 

 experiments in Chapter VI., will not become green by the application 

 of an iron salt solution. This fact of the utilization of iron applied to 

 the surface of a chlorotic leaf is referred to by Sachs (1887, p. 285). 

 This same result was obtained some years ago in the case of a Maize 

 plant, by Miss Minns at the physiological laboratory. Botany Garden of 

 Harvard University. Definite information regarding this experiment 

 the writer has not been able to obtain. 



Summarizing the results of the experiments here described we may 

 conclude that : — 



(i) Salts in solution are absorbed through both surfaces of leaves of 

 plants whether the leaves be detached or not if the surrounding atmos- 

 phere be favourable. Absorption generally takes place more readily 

 when the solution is applied to the lower surface. 



(2) Dilute solutions applied in drops stimulate the leaf tissue in a 

 ring, whereas if the solutions are concentrated the entire area covered 

 by the drop is affected. 



(3) The effects produced by poisonous solutions upon Spirogyra aid 

 in explaining the effects of similar solutions upon foliage leaves. 



