234 



NATURE 



[August i8, 192. 



The Ascent of Sap. 



The Physiology of the Ascent of Sap. By Sir Jagadis 

 Chunder Bose. (Cossimbazar Endowment Publica- 

 tion.) Pp. XV + 277. (London: Longmans, Green 

 and Co., 1923.) x6s. net. 



THE author supplies in this book further ingenious 

 experimental devices in which use is made of 

 automatic recording methods and of various methods 

 of magnifying small movements. The rate of ascent 

 of sap is measured by a mechanical method recording 

 the re-erection of a drooping tissue as sap enters it, 

 and by an electrical method in which a quadrant 

 electrometer is used to determine change of electro- 

 motive force between two points, one of which 

 changes in turgor. By placing one electrode, carefully 

 insulated save at the point, upon a graduated micro- 

 meter screw movement, the instrument becomes an 

 electric probe by which the most vigorous changes in tur- 

 gor are traced in the Dicotyledon stem to the living tissues 

 in the region between inner cortex and vascular tissue. 



The usual simple potometer experiment is modified 

 into a recording potograph, whilst an ingenious bubbling 

 method is introduced to measure the absorption of 

 water by a cut shoot, and thus indirectly its tran- 

 spiration, under varying conditions. 



Many interesting observations are recorded in this 

 account of work in the Indian climate, notably the 

 report upon the exudation of sugar solution from 

 cut surfaces in the stem apex or the inflorescence of 

 the palm. This exudation is shown to be quite inde- 

 pendent of any direct supply of sap from the absorbing 

 system of the root. 



The author's attempt to reinterpret the phenomena 

 of the ascent of sap in the light of his new experiments 

 is not convincing. As the result of a discussion of 

 earlier work, mainly based apparently upon the Enghsh 

 translations of the text-books of Haberlandt, Jost and 

 Pfeffer, it is concluded that transpiration from the 

 leaf and exudation from the root do not provide an 

 adequate mechanism for the ascent of sap, whilst the 

 role of osmosis is dismissed in two paragraphs. As 

 opposed to this inadequate mechanism is advanced 

 " a theory of cellular pulsation according to which the 

 hquid is injected by the living cells into the wood- 

 vascular tissue." 



Later, the role of the xylem vessel seems practically 

 to disappear — " The uni-directional propulsion of sap 

 depends upon a sequence of pulsation from cell to cell. 

 The sap expelled during the contraction of any one 

 cell is absorbed by a cell higher up during its phase of 

 expansion. There is then a propagation of a wave of 

 contraction, preceded by one of expansion, in conse- 

 quence of which the sap is, as it were, squeezed forward. 



NO. 2807, VOL. 112] 



A succession of such waves maintain the continuous 

 ascent of sap." Though this may Ije clear to the 

 author, the reviewer feels himself no nearer an under- 

 standing of the actual movement of sap in the plant. 

 The demonstration of this mechanism rests upon 

 experimental evidence that temperature, poisons, and 

 various other external factors affect similarly sap 

 movement and the pulsating mechanism, and upon a 

 demonstration of electro-motive forces in tissues which 

 are assumed to be manifestations of changes in cell turgor. 

 The experimental evidence is, however, not employed 

 critically ; thus it is argued that transpiration is not 

 essential to the ascent of sap because the author's 

 mechanical method shows a rapid rise of sap in a 

 partially wilted chrysanthemum shoot when the cut 

 end is placed in water, although the surface, both stem 

 and leaf, had previously been coated with vaseline. 



A Metric Campaign. 



World Metric Standardisation : An Urgent Issue. A 

 Volume of Testimony urging World-wide Adoption of 

 the Metric Units of Weights and Measures — Meter- 

 Liter-Gram. Compiled by Aubrey Drury. Pp. 524. 

 (San Francisco : World Metric Standardisation 

 Council, 1922.) 5 dollars. 



FOR several years an intensive propaganda has 

 been carried on by the " World Metric Standard- 

 isation Council " on both sides of the Atlantic in 

 furtherance of the objects indicated in the title of 

 this book. Apparently self-appointed, its executive 

 includes a number of men prominent in poUtics, 

 commerce, and engineering, mainly resident in the 

 United States, but representing also Canada and 

 Great Britain, and the council has members and 

 correspondents in almost all countries. It is under 

 the direction of this body that the volume before us 

 has been compiled, bringing together a vast amount 

 of information and data regarding the " master 

 standards " of the world, and aiming, of course, to 

 promote their adoption in the United States and the 

 British Empire for all commercial transactions. It 

 is pointed out in the introduction that far less 

 opposition has been raised to the adoption of the 

 litre and gram than to the metre, which is very much 

 more closely related to industrial processes than the 

 units of mass and volume ; but on the other hand, 

 it is not proposed to impose the use of metric measures 

 upon production — only upon distribution. 



A large proportion of the work consists of quotations 

 from the reports of committees which have investigated 

 the subject at various times, the writings and speeches 

 of individuals, and Bills which have been introduced 

 into Congress and Parliament, as well as resolutions 



