10 Scientific Proceedings, Royal Dublin Society. 
branch in each experiment showed signs of wilting. When the 
supply through the dead branch was cut off, either by the with- 
drawal of the water from its end, or by its own clogging, the 
wilted leaves partially recovered. But in several experiments the 
edges of the leaves were too far injured to recover, and the injury 
persisted as a brown margin on the leaf. 
The experiment may also be carried on with a straight branch 
from which the upper leaves and side branches are removed. The 
stripped upper portion is immersed for a short time in water at about 
95° C., and after death so caused, water is supplied through this 
dead portion to the lower leaves and side branches, which have 
been left undisturbed. If the supply of water through the upper 
dead part of the branch is kept up, fading and partial withering 
of the leaves below will be noticeable in a few days. 
Inasmuch as the effect on the leaves depends on the amount of 
harmful matter carried up from the dead cells, it is evident that 
immediate or complete withering is not to be expected, for the 
supply from the dead part is largely diluted with the supply from 
the roots through the living, and, also, it is difficult to make the 
supply through the dead part considerable owing to the clogging 
at the cut surface, and also possibly owing to internal clogging 
caused by the exudations into the water-capillaries from the dead 
cells. 
Another and simpler method of observing the withering effects 
of the substances liberated from cells, when killed by heat, may be 
carried out as follows:—A decoction is made by boiling small 
pieces of a stem in water for a short time. This decoction, after 
repeated filtering, is supplied to cut branches of the same tree. 
It will be found that the leaves of the branches supplied with 
the decoction fade and wither much more rapidly than those 
of control-branches supplied with water. For example, three 
branches of Syringa vulgaris, set in a decoction of the stem of the 
same plant, lost their turgidity within two days, while the leaves 
of three control-branches were still fresh after five days. 
Taken alone, this last observation would not be sufficient to 
prove that in intact branches the withering of the leaves is due to 
deleterious substances emerging from the killed cells ; for it might 
be urged that colloid substances in the decoction aggregating on 
the cut surface obstruct the free transmission of water, and thus 
