8 Scientific Proceedings, Royal Dublin Society. 
these latter were richly supplied with water, shows that the living 
elements which had been destroyed by the heat were needed to 
raise sufficient water to keep the leaves turgescent. 
Furthermore, he carried out similar experiments himself on a 
smaller scale, and found that, when very short pieces (only 2-3 
ems.) of the supporting branch were killed, practically no harmful 
effect is noticed on the leaves. If longer pieces are killed, wilting 
and withering quickly supervene. Ursprung’s experiments 
differed from Strasburger’s, and resembled Janse’s in the fact 
that the branches experimented upon were left attached to the 
plants, and consequently were connected to the root during the 
experiments. 
As the resu!t of his observations he concludes that the living 
elements of the stem do participate in the elevation of the sap 
directly by lifting and supporting the water, and also in some 
cases indirectly by maintaining the water-ways in a condition 
suitable for conducting water. The latter conclusion he bases on 
the observation that when loss of water from the surface of the 
dead stem was prevented by a coating of paraffin, sometimes the 
harmful effects on the leaves above were less noticeable. 
T venture to think, however, that the experimental facts, which 
Ursprung believes to support his views, could find a more satis- 
factory explanation in other ways. 
For example, if we accept the view that the ascending current 
isin a tensile state, it is quite conceivable that the high temperature 
needed for killing the cells would sufficiently lessen the cohesive 
strength of the water, by increasing its vapour-pressure, and so 
cause rupture in most or all of the water-columns. When a 
short region only is killed by heat, the “bleeding ”’ pressure of 
the remaining living cells would be adequate to restore con- 
tinuity; while if the discontinuities extend through great lengths 
of the stem, the ruptures cannot be made good before the 
diminished supplies cause the leaves to fade. 
Another possibility suggests itself. The cells killed by the 
action of the heat may give up substances in solution to the trans- 
piration current which either may act as poisons to the leaf-cells, 
or which, by concentrating in the leaves, may act as plasmolysing 
agents on the cells of the leaves, and cause the fading of the 
leaves. The fact that a minimum length of the stem must be 
