20 TRANSPIRATION AND ASCENT OF SAP ch. 



was drawn up into living specimens placed side by side 

 with the dead ones. The dead branches which I used 

 had been killed by chloroform vapour, or by immersion 

 for some minutes in water at 90 C. 



In these experiments when the coloured fluid was drawn 

 up only into the capillaries of the stem, the pumping action 

 raising it may have been exerted either by the cells 

 bordering the conduits in the stem, or by those in a similar 

 position in the leaves. But when the veins of the leaves 

 become injected, it is evident, since no cells interrupt the 

 continuity of the water-conducting capillaries, that some 

 of the cells exerting the traction in the fluid must be 

 situated in the leaves. 



This fact may be demonstrated more directly by experi- 

 ments in which the ascent of watery eosin in a branch 

 stripped of its leaves is compared with that in a similar 

 branch provided with leaves, when both are placed in the 

 saturated chamber. It will be found I have performed 

 the experiment with Chrysanthemum sinense, Escallonia 

 macrantha, Cheiranthus cheiri that the leafv branch will 

 draw up the eosin rapidly, while in similar circum- 

 stances the colouring matter will rise but slightly a few 

 cms. per hour in the branch deprived of its leaves. The 

 rise observed may be easily explained by the supposition 

 that, in the green parts of the young branches and the 

 buds, the cells probably act like those of the leaves, and 

 draw up water ; or, again, the action of the cells border- 

 ing the capillaries of the stem wood-parenchyma and 

 medullary rays may be responsible for the elevation 

 observed. In any case the rise is but slight, 3-5 cm. in 

 the stripped branches, compared with 20-30 cm. in the 

 leafy branches during the same time. 



That the elevating force is chiefly located in the leaves 

 may also be shown by the fact that large leaves detached 

 from the stem are capable of quickly injecting the finest 

 veins at their apices when set upright in watery eosin in 



