540 RESPIRATION AND FERMENTATION 



tissues may be insufficiently supplied with oxygen even in ordinary air 

 (cf. Sects. 29-32). The respiratory exchanges are especially active in 

 bacteria, and sulphur-bacteria are able to obtain the large amounts of 

 oxygen they require in exceedingly dilute form 1 . When a seedling 

 is suddenly placed in air containing only 3 to 4 per cent, of oxygen intra- 

 molecular respiration commences, and a volume of carbon dioxide is evolved 

 \vhich greatly exceeds the amount of oxygen absorbed. After a time, 

 however, the plant accommodates itself to the changed conditions, and in 

 twenty-four hours the same supply of oxygen may suffice for the diminished 

 respiratory activity ~. 



Similarly when the partial-pressure of oxygen is increased to an excessive 

 extent death ultimately ensues, and respiration perforce ceases. Many plants, 

 especially among Phanerogam s, continue at first to respire and grow at 

 almost the normal rate under a pressure of twenty to thirty atmospheres, 

 but in only a few hours both functions gradually diminish and ultimately 

 cease at the onset of death, which occurs after several hours or days a . 

 Under such circumstances seeds and spores are unable to germinate. 

 Many of both the higher and the lower plants develop normally in pure 

 oxygen or in air under a pressure of five atmospheres 4 . There can be no 

 doubt that all grades of sensitiveness to oxygen are exhibited throughout 

 the vegetable kingdom, connecting these highly resistant forms with those 

 to which the presence of a trace of oxygen is fatal. Thus sulphur-bacteria 

 are strongly aerobic but require and indeed prefer the presence of traces 

 of oxygen only, and although a very small amount of this gas is fatal to 

 certain obligate anaerobes (Bacillus polypifonnis, B. ocdcmatis maligni, 

 Spirillum desulfuricans], others may continue to grow even in the presence 

 of a little of it ( Clostridium foetidmn, Granitlobacter butylicinnY- According 

 to Beyerinck the last-named organism grows best when supplied with a little 

 oxygen if cultivated upon starch-paste and peptone, and Kitt 6 has found it 

 possible to cultivate Bacillus carbonis upon bouillon in air, although Migula 



1 \Yinogradsky, Bot. Zeitung, 1887, p. 539; Bcitr. z. Morph. u. Fhysiol. d. Bact., 1888, I, p. 50. 

 Red sulphur-bacteria can obtain oxygen by CO 2 -assimilation, and hence remain living for weeks if 

 exposed to light in closed oxygenless tubes containing a little H 2 S and a trace of reduced indigo- 

 carmine. Cf. Engelmann, Die Purpurbakterien, Bot. Zeitung, iSSS, p. 661 ; Ewart, Journ. of Linn. 

 Soc., 1897, Vol. xxxni, p. 153. 



2 Stich, 1. c., p. 13 ; Gcdlewski, Jahrb. f. wiss. Bot., 1882, Bd. xni, p. 522. 



3 Johannsen, Unters. a. d. Bot. Inst. z. Tubingen, 1885, Bd. I, p. 716 ; Jentys, ibid., 1888, Bd. i, 

 p. 457. On bacteria, cf. Wossnesenski, Compt. rend., 1884, T. xcvin, p. 314. 



* Cf. Johannsen u. Jentys, 1. c. ; also Jaccard, Rev. gen. d. Bot., 1893, V, p. 383, and the literature 

 here quoted. On bacteria, Frankel, Centralbl. f. Bact., 1889, Bd. V, p. 210. 



5 Cf. Liborius, Zeitschr. f. Hygiene, 1886, Bd. i, pp. 168, 170; Beyerinck, Centralbl. f. Bact, 

 1895, Abth. ii, Bd. I, p. 109; Uber die Butylalkoholgahrung, 1893, p. 45. 



6 Kitt, Centralbl. f. Bact., 1895, Bd. xvn, p. 168. On the influence of different substances upon 

 anaerobiosis, cf. also Kitasato u. Weyl, Zeitschr. f. Hygiene, 1890, Bd. vili, p. 41 ; Bd. IX, p. 17. 



