546 RESPIRATION AND FERMENTATION 



produced by treatment with o-ooi to 2 per cent, solutions of hydrogen peroxide. 

 In such dilution the latter is innocuous, but it causes the cell-sap in the roots of 

 Vicia faba to turn brown, and decolourizes the purple pigment in the cell-sap 

 of the staminal hairs of Tradescantia. Such changes are permanent when once 

 induced, and hence the feeblest oxidatory action in the cell-sap would ultimately 

 become perceptible. Similarly no active oxygen is present in the protoplasm, 

 for when permeated with cyanin, the latter undergoes no oxidation, which however 

 at once ensues when a little hydrogen peroxide is added '. 



The transference of oxygen from an absorbent substance to one which is 

 oxidized does not involve any ozonization, nor does this occur in those pigment- 

 bacteria which Ewart's researches have shown to be capable of entering into 

 a loose combination with oxygen similar to that formed by haemoglobin*. The 

 oxygen absorbed apparently unites with the excrete bacterial pigment which remains 

 in close association with the bacterial colonies, and hence the pigment not only plays 

 a most important part in the transference of oxygen to the living and aerobic bacteria, 

 but also conveys oxygen to the interior of the colony. The oxygen thus stored up 

 does not, however, suffice for more than a few hours' respiration. In ordinary plants 

 no oxygen is stored in this manner as a compound which slowly dissociates when 

 the partial-pressure is reduced, for when all free oxygen is removed rotation soon 

 ceases, although it can continue when the oxygen partial-pressure is extremely 

 low (Clark, Ber. d. Bot. Ges., 1888, p. 273). In certain cases streaming movements 

 persist for a longer time, but this may simply be a manifestation of the energy 

 derived from intramolecular respiration and does not necessarily prove that any 

 oxygen is held by such cells in occluded form. [Cf. Ewart, 1. c., p. 145, and 1896, 

 Vol. xxxi, p. 420. Kiihne (Zeitschr. f. Biol., Bd. xxxv, 1897, p. 43; 1898, p. i) 

 states that streaming may continue in Nitella as long as fifty days in darkness, and 

 concludes on insufficient grounds that a store of oxygen must be present in the 

 living cells. The explanation seems to be, however, that Nitella is a partial 

 anaerobe. In any case the results are in urgent need of confirmation, for a very 

 minute trace of oxygen apparently suffices to maintain rotation in Chara for an 

 almost indefinite length of time. Cf. Ewart, 1. c.] 



SECTION 102. The Relationship between Aerobic and Anaerobic 



Respiration. 



The withdrawal of oxygen causes metabolism to assume a different 

 character, and may thus lead to the formation of products which did not 

 previously appear, either owing to the awakening of dormant powers, 

 or, as is more probably the case, because under the new conditions the 



1 Pfeffer, Oxydationsvorgange, 1889. On the poisonous action of H,O 2 , cf. Kny, Ber. d. Bot. 

 Ges., 1889, p. 165 ; Fliigge, Mikroorganismen, 1876, 3. Aufl., Bd. I, p. 461. Ozone is much more 

 poisonous. Cf. Pfeffer, 1. c., p 427 ; Fliigge, 1. c., p. 461. 



' Ewart, Journ. of Linn. Soc. Bot, 1897, Vol. xxxin, p. 123 ; Abstract by Pfeffer in Ber. cl. 

 Sachs. Ges. d. Wiss., 1896, p. 379. 



