470 Scientific Intelligence. 



this it has been shown that the production of wood in a slowly 

 growing tree is greater than is necessitated by mechanical 

 requirements. In other words, the production of new wood is 

 largely determined by the length of time during which the 

 wood-parenchyma can remain active. 



There is no known means by which these cells can directly 

 pump water in a definite direction, although the existence of a 

 power of absorbing and exuding water under pressure has been 

 empirically determined to exist in the living wood of cut 

 branches. It is suggested that the wood-parenchyma cells 

 by the excretion and re-absorption of dissolved materials may 

 bring into play surface-tension forces within the vessels of suffi- 

 cient aggregate intensity to maintain a steady upward flow, and 

 to keep the water of the Jamin's chains in the vessels in a mobile 

 condition ready to flow to wherever suction is exercised upon it.* 

 The rapid rates of diffusion required for such action do actually 

 exist in the wood-parenchyma cells. 



It appears that the terminal branches of trees at heights of 

 from 22 to 44 feet above ground exhibit little or no power of 

 bleeding in spring. Possibly in such trees the pumping action 

 is only used or developed in the wood of the older stems, or is 

 only exercised when transpiration is active, and when the water- 

 columns in the vessels attain a definite size relatively to the 

 wood-parenchyma cells. The importance of the Jamin's chain in 

 the vessels is that it renders a staircase-pumping action possible, 

 and enables the water to be maintained in the vessels in a labile 

 condition, ready to flow to any point where moderate suction is 

 exercised. This pumping action being diffused and probably 

 regulated, need not produce any high pressure of exudation at 

 the terminal branches of tall trees, which, in fact, appears always 

 to be absent at high levels. — JProc. Hoy. /Soc, lxxiv, 554. 



2. Problems of the Panama Canal; by Brig.-Gen. Henry L. 

 Abbot, IT. S. Army, retired. 248 pp. New York, 1905 (The 

 Macmillan Co.). — The position occupied for so many years by 

 General Abbot in the Engineer Corps of the United States Army, 

 and also his official connection with the new French company for 

 the Panama Canal established in 1894, have made him particu- 

 larly fitted to give an accurate and thorough presentation of the 

 more important scientific problems involved in the present and 

 future work on the Canal. The volume is a particularly timely 

 one, and will be read with interest by the general public, as well 

 as by those more immediately concerned. A brief historical 

 introduction is given, followed by a chapter on the relative 

 advantages of the two routes which have been discussed ; to that 

 of Panama unqualified approval is given. The bulk of the work, 

 however, is devoted to the consideration of the peculiar physical 

 conditions existing on the Isthmus, particularly those affecting 



* Surface-tension actions would be possible in the absence of air-bubbles 

 wherever the wood-parenchyma cells contained oil or any other substance 

 non-miscible with water, as they often do. 



