328 LIFE : OUTLINES OF GENERAL BIOLOGY 



down of the leaf. Distinguished from this is the effect of indirect 

 stimulation of feeble intensity, for it implies increase of turgor, 

 expansion, accelerated rate of growth, and the positive response — 

 the erection of the leaf. Here, we confess, the alert experimenter 

 moves too quickly for us. 



(3) Very striking— we wonder how it had been missed — is the 

 observed fact that an excitation may pass up one side of the stem 

 and down the other. 



These are three of the many new facts expounded in Bose's fascin- 

 ating volume, the main result of which is the certainty that the plant 

 is a more "nervous" organism than has been supposed. But behind 

 the facts is the interpretation. The conduction of the excitation is 

 probably by elongated cells of the phloem and the bundle-sheath as 

 it is called, but the analysis of the path does not prove that these 

 elements are in the strict sense nervous. We cannot go further than 

 say that in our judgment Bose works out a very suggestive parallel 

 between the conducting system in plants and the nervous system 

 in animals. But we do not think that he allows enough for the 

 alternative interpretation in terms of the diffusion of fluids and 

 of the hormones which they may contain. The work of Ricca and 

 of Snow demands fuller consideration. But even if Sir Jagadis's 

 interpretation fails to convince, his facts are illuminating. He 

 corrects LinucTus : Vegctabilia sentiunt. 



THE ORGANISM AS MECHANISM, YET MORE.— It is an old 



story, as biology goes, that the green plant seizes and applies the 

 energy of light to its nutritional and constructive advantage, and is 

 thereby physiologically distinguished from ordinary animals, and 

 from such non-chlorophyllian plants as moulds and mushrooms. 

 Bergson however (in Creative Evolution, Chap. II) has made fuller 

 use of this familiar conception for his criticism of the strictly 

 mechanistic view of physiological processes; and Prof. Johnstone, 

 in his valuable Philosophy of Biology (1914) and in The Mechanism 

 of Life (1921). has developed this criticism with vigour and fullness. 

 The general ])rocesses m non-living or physical Nature and of 

 man's machines agree in running down, and that irreversibly, 

 towards that degradation of energy which Kelvin called its dissipa- 

 tion, but which is better described as from minimum to maximum 

 entropy— that inertness of universally uniform temperature, the 

 "warm-death" (Warmetod) of Clausius, in which all phj'sical pro- 

 cesses seem as yet destined to end, so far as the doctrine of energy 

 yet goes. 



But the processes of life- and these not only in the green leaf, but 

 in various measure throughout all constructive metabolism, of animal 

 and plant alike— exhibit a reversal of this process; so we have here 

 a diagnostic character between living beings and the inorganic world. 



