*630 Proceedings of the Royal Irish Academy. 



As we would expect, it was found that, when dead leaves and 

 tranches were set in this saturated chamher, no rise of the eosin was 

 observed, although simultaneously eosin 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 dischai'ged 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 inter- 

 rupt the continuity of the water- conducting capillaries, that the cells 

 exerting the traction in the fluid must be situated in the leaves. 



This fact may be more directly demonstrated by experiments 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 Chryscmthemum sinense, Escallonia 

 macranthttj Cheiranthus Cheiri — that the leafy branch will draw up 

 the eosin rapidly, while under similar circumstances 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 by a pumping action ; 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 cms. in the stripped branches, compared with 

 20-30 cms. 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 ajsex when set 

 upright in watery eosin in the saturated chamber. For this purpose 

 I used the leaves of Eucalyptus ylohulus, and found that their apical 

 veins were injected often after standing only 30 min. in eosin, and 

 surrounded with a saturated atmosphere. The eosin, to do this, had 

 risen 20 cms. in the leaf above the level of the solution in which the 

 leaf stood. In this case it is evident that the cells of the leaf must 

 have been solely responsible for the observed elevation. 



But the directed pumping actions which cause the elevation of the 

 coloured fluid in these cases, although mostly confined to the leaf, do 



