Flood — Exudation of Water by Colocasia antiquorum. 511 



But action continued at the same rate, so the water must be urged forward 

 from the plant and not be produced by glands at the tips of the leaves. 



That there is a liberal supply of water sent up to the leaves is shown by 

 the following observations :— If a vigorously acting leaf be cut anywhere — 

 across the lobes, across the middle of the blade, or round the point of insertion 

 of the petiole — there is copious exudation from the veins at every cut, and 

 from the canals. The cut surfaces may be plugged with mucilage after a 

 time ; but before this happens, whenever there is vigorous action going on 

 in other leaves, exudation will recommence from these surfaces. Exudation 

 from cut surfaces also occurs in the petioles. One evening, about 9.30, 

 when action was going on very vigorously, water was noticed pouring from 

 the cut end of the petiole from which the blade had been removed a few days 

 previously. The surface was nearly horizontal, but the quantity of water was 

 so great that it could be seen running down as a stream on the side of the 

 petiole. A cut was made at the very base of this petiole, and water spurted 

 out. The same thing happened when cuts were made at the bases of others. 



Some roots were cleaned free from soil, with the exception of their apical 

 regions, in the morning, and surrounded with Sphagnum moss, while still 

 attached to the plant. That night, when action was vigorous, they were cut 

 off from the plant, but there was no exudation of moisture from their cut 

 surfaces. Possibly shock had checked exudation. This was repeated several 

 times with roots that had not been previously disturbed, and in every case 

 drops of moisture were apparent on their cut surfaces, and when wiped 

 away more gathered. Although each root produced very little water, still, if 

 a few hundred roots were supplying the plant from a damp soil, and if the 

 atmosphere were saturated, both of which conditions were obtaining, the 

 quantity of water supplied to each leaf would be appreciable. 



The conclusions that may be drawn from these observations and experi- 

 ments are that there is no special tissue in the leaf-tip which mio-ht be 

 described either as a gland or epithem for the secretion. Neither is there 

 any membrane intervening between the water-channels and the depression in 

 the leaf for filtering the water. Arrangements have been made for the 

 transfer of water through the plant, so it seems that cells lower down in the 

 plant must be responsible for the secretion and filtration of the water ; and 

 there seems no evidence for the existence of special cells for this function 

 outside the root. 



[Eeferences. 



