in ASCENT OF SAP IN STEMS 63 



cold water supplied through it to the leaves supported 011 

 the uninjured branch. These leaves then drew supplies 

 of water from two sources, viz., from the roots, and through 

 the dead branch. To facilitate this latter supply a fresh 

 surface was occasionally cut on its distal extremity. The 

 length of the dead branch in my experiments varied from 

 30 to 40 crn. Notwithstanding the double supply of water, 

 the leaves on the living branch in each experiment showed 

 signs of wilting. When the supply through the dead branch 

 was cut off, either by the withdrawal 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, and after death 

 so caused, water is supplied through it to the lower 

 leaves and side branches, which have been left un- 

 disturbed. 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 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, furthermore, it is difficult to make the supply through 

 the dead part considerable owing to the clogging at the 

 cut surface, and to the internal stoppages 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 



