316 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



maximum at 50 C. Probably motile thermo-bacteria may remain capable 

 of movement at 70 C. and over, and certain Oscillarias and Diatoms above 

 50 C. Most Bacteria, Infusoria, Vorticellae, and Rotifers cease to move, 

 sooner or later, at from 40 to 45 C. l 



A sudden change of temperature may awaken streaming in quiescent 

 cells 2 , and may produce a more or less pronounced disturbance in cells 

 which already show streaming. This may be evidenced either by a 

 temporary acceleration or retardation or by a succession of both. A rapid 

 rise to a supraoptimal temperature commonly produces an irregular feverish 

 activity of streaming 3 . A sufficiently sudden and pronounced rise or fall 

 of temperature always produces a temporary or permanent shock-stoppage 

 of streaming in cells which normally show this form of activity ; but if 

 the streaming has been induced by previous stimulation, the superimposed 

 effect of a sudden change of temperature is naturally less evident 4 . It was 

 probably owing to this reason, and to the insufficient rapidity with which 

 the temperature altered, that Velten 5 was unable to detect any shock- 

 disturbance at all. The existence of a shock-effect is well shown by the 

 fact that localized cold or heat suddenly applied to one end of a cell 

 of Chara or Nitella causes a temporary stoppage of streaming over the 

 entire cell. 



In all cases, however, the protoplasm rapidly accommodates itself to the 

 new conditions if their action is not of too great intensity. Thus when 

 streaming is resumed after the application of localized cold 6 , it is slower 

 in the cold area largely owing to the higher viscosity of the endoplasm 7 , 

 and this causes an accumulation of protoplasm at that point. 



Schultze, Kiihne 8 , and Sachs 9 observed that exposure to high or low 

 temperatures produced a pronounced deformation, fragmentation, or vacuo- 

 lation of the protoplasm, such as may also be caused by the action of 

 induction-shocks or poisons. Klemm 10 found that these changes only take 

 place when the cell is returned to a normal temperature, and that they may 

 be accompanied by spasmodic feverish streaming until the cell becomes 

 normal again. The return to a normal temperature appears, therefore, 



1 Ewart, Protoplasmic Streaming in Plants, 1903, p. 62. A few details concerning Oscillaria 

 are given by Meyen, Pflanzenphysiologie, 1832, Bd. Ill, p. 565 ; on antherozoids see Hofmeister, 

 Pflanzenzelle, 1867, p. 33, and Voegler, Bot. Ztg., 1891, p. 675. 



1 Hauptfleisch, Jahrb. f. wiss. Bot., 1892, Bd. xxiv, p. 210. 



3 Dutrochet, Ann. sci. nat., 1838, p. 27 ; Hofmeister, 1. c., p. 53 ; Kiilme, Unters. ii. d. Proto- 

 plasma, 1864, P- Io2 ; de Vries, Materiaux p. la connaissance de I'influence de la temperature s. 1. 

 plantes, 1870, p. 8 (reprint from Arch. Neerlan daises, T. v) ; Klemm, Jahrb. f. wiss. Bot., 1895, 

 Bd. xxvm, p. 640; Hermann, Studien ii. d. Protoplasmastromung bei d. Characeen, 1898, p. 45. 



4 Ewart, 1. c., p. 66. The same effect may be produced by feeble etherization. Josing, 1. c., 



p. 2JO. 



* Velten, Flora, 1876, p. 214. 



6 Hormann, 1. c., p. 46 ; Ewart, 1. c. 7 Ewart, 1. c., p. 48. 



8 Kuhne, 1. c., pp. 64, 87, 101. Sachs, 1. c., pp. 39, 66. 10 L. c. 



