256 



Transactions of the Canadian Institlte. 



[Vol. VII. 



trichomes in Primula (Fig. 5, i) serve a similar purpose. The tissue 

 next the epidermis over the veins in Ampelopsis is composed of thin- 

 walled parenchyma cells without chlorophyll (Fig. 10, H). Just how 

 far one is justified in reasoning from anatomy to function is not 

 easy to say. These anatomical conditions are not mentioned as 

 proof, but as evidence in favour of absorption. 



Stahl has endeavoured to show that corrugations and hairs over 

 the veins, aid in shedding water, but this does not accord with the 



results of the experiments per- 

 formed by the writer and recorded 

 in Chapter VII. The hairs along 

 the veins, by capillary action, 

 cause solutions to ascend the 

 petiole and pass out over the veins 

 to such an extent that the leaf 

 becomes coated with salt when the 

 water evaporates. Henslow (1888) 

 and Garreau (1851) held that such 

 corrugations and hairs over the 

 veins aided in absorption, as well 

 as in spreading drops of water 

 over the leaf. 



It is shown elsewhere in this 



paper that solutions are absorbed 



by leaves even when the plant is in 



PIG ,_ a saturated atmosphere (Chapters 



VI. and VII.). 



(i). A semi-perspective view of a trichome of 

 Primula stellata, partially laid over tow.irds one 

 side showing trichome Tr. in part; Chloroplasts, 

 ch. ; striations, St. ; surface view of epidermal 

 cells, Ep. 



(2). Optical section of a trichome Tr. ; part 

 view of cross section of petiole showing basal 

 cell Bl. of trichome, also epidermal layer and 

 parenchyma Pa. 



The evidences in support of 

 water absorption by leaves upon 

 the plant may be summarized as 

 follows : — Detached leaves absorb 

 water, and since they function, in a 

 measure, as when attached to the living plant (Chapter VII.), it 

 may be concluded that attached leaves absorb. Dilute solutions are 

 absorbed, and therefore water viay be absorbed. Certain anatomical 

 structures make it seem probable. Since distilled water will extract 

 inorganic salts from leaves, it follows that water may enter the tissue 

 during the process. The historical evidence is overwhelmingly in 

 favour of absorption. Since substances contained in water of guttation 



