K.— BOTANY 217 



tissues ; the movements of the protoplasm also cease if the surrounding 

 air is deprived of this gas ; and the power of motion possessed by 

 periodically motile and irritable organs is lost if oxygen is withheld from 

 them ; but if this happens only for a short time the motility returns when 

 the oxygen is again restored.' This is, as far as I am aware, the first 

 reference to the fact that respiration is a constant function of cell activity. 

 Although this doctrine has been accepted without adequate proof, it 

 must be admitted that no evidence has been adduced against it and it 

 has never been disputed, and it is clear that respiration is as much part 

 of the field of general cell physiology as the absorption and excretion of 

 water and dissolved substances. Although Sachs is thus to be credited 

 with establishing the view of the constant incidence of respiration in cell 

 activity, neither he himself nor his pupils contributed a great deal towards 

 the elucidation of the respiratory mechanism nor to the part played by 

 it in cell activity, although a few important investigations were made in 

 his laboratory, and later in that of his pupil, Pfeffer. The greatest 

 activity in this field was displayed by Russian investigators, and, com- 

 mencing in 1875, there has issued a constant stream of records of re- 

 searches on plant respiration from Russian workers, among whom 

 Palladin and Kostytschev were particularly conspicuous. 



As work on respiration proceeded it came to be more and more supposed 

 that enzyme activity played a leading part in the respiratory process. 

 But it must be admitted that whereas during recent years considerable 

 advances have been made in elucidating enzyme systems in animal cells 

 and relating them to the processes of respiration, the part played by such 

 systems in plant respiration is still rather a matter of speculation than of 

 indisputable fact. Indeed, in spite of much careful and painstaking work, 

 our knowledge of the enzyme systems themselves is still very chaotic. 



If experimental observations have been interpreted aright, and if it is 

 a fact that every living cell respires, then we must conclude that respira- 

 tion is something most inextricably connected with 'life. Yet it seems to 

 me that explanations of the function of respiration in the plant are not 

 altogether satisfying. Let us examine the views of the great authorities 

 of the past on this question. Sachs wrote : ' The loss of assimilated 

 substance caused by respiration would appear purposeless if we had only 

 to do with the accumulation of assimilated products ; but these are 

 themselves produced only for the purposes of growth and of all the 

 changes connected with life ; the whole of the plant consists in com- 

 plicated movements of the molecules and atoms ; and the forces necessary 

 for these movements are set free by respiration. The oxygen, while 

 decomposing part of the assimilated substance, sets up important chemical 

 changes in the remaining portion, which on their part give rise to diff'usion 

 currents, and these bring into contact substances which again act chemi- 

 cally on one another, and so on. The dependence on respiration of the 

 movements in protoplasm and motile leaves is very evident, since, as has 

 been mentioned, they lose their motility when oxygen is withheld from 

 them. These considerations lead to the conclusion that the respiration 

 of plants has the same essential significance as that of animals ; the 

 chemical equilibrium of the substances is being constantly disturbed by 

 it, and the internal movements maintained which make up the life of the 



