the Ascent of Water in Trees. 649 
and formulated the significance of the cohesion of water in the ascent 
of sap.’ 
A further matter for consideration suggested itself over and above 
those enumerated; a collateral question, it is true, but one neverthe- 
less of great interest and importance : — What is the nature of the 
suction-force in the leaf? 
Our earlier ideas led us to the view that capillary actions and the 
phenomena of evaporation were mainly concerned with the upholding 
and raising of the sap, as will be more fully gone into further on. 
I gather from Professor Askenasy’s papers that, in so far as we regard 
capillary phenomena (or as he prefers to call them £ imbibition ’ 
phenomena) as upholding the sap, we were then in accord with his 
present views. He claims priority for these views, however, giving 
as his reason that they are not so definitely stated in our Abstract as 
in our full paper, and, perhaps misled by the term ‘ revised ’ occurring 
at the head of our complete paper, insinuates that we borrowed them, 
in their more pronounced statement, from his paper of February, 1895. 
(See pp. 19, 20, Beitrage zur Erklarung des Saftsteigens.) 
This accusation is easily disposed of. I quote (translating) in full 
from Professor Askenasy’s paper : — 
£ I come now to the imbibition of the cell-wall, the other 1 chief 
factor in the ascent of sap, from which the true (eigentliche) sucking 
action proceeds. The imbibition force of the cell-wall is in fact the 
so long vainly sought for source of the suction-force concerned in the 
ascent of sap in the plant. I believe myself to be the first to point 
out clearly the importance of imbibition in the ascent of sap, since 
Dixon and Joly speak of it in their first communication in a quite 
uncertain manner : — ££ Whether the draught upon the sap established 
at the leaf during transpiration be regarded as purely capillary or not, 
their experiments lead the authors to believe that it alone is adequate 
to effect the elevation by direct tension of the sap in tall trees.” 
£ In the complete communication which appeared after my first 
work it runs for the first time thus : — “ The meniscuses are formed in 
the membranous re'seau of the evaporating cell-walls, while the columns 
of liquid supplying the evaporation loss exist in the functioning 
conduits.” ’ 
It will be seen that the quotation from our complete paper is advanced 
1 Refers to the stability of a liquid in tension and containing gas in solution. 
X X 
