342 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



nitrous oxide, Demoor's l statement that aerobic plants continued to show 

 streaming in this gas can be regarded as a proof that the gas used con- 

 tained free oxygen 2 . 



Kiihne 3 considered the long continuance of anaerobic streaming in 

 Characeae to be due to the presence of a store of occluded oxygen, but 

 Ewart 4 has shown that this is not the case. 



Poisons. Every substance which influences metabolism may also 

 influence streaming 5 , either directly or as an after-effect, and apart from 

 any retardation or stoppage produced as the effect of the shock of a sudden 

 change. Many substances when dilute, such as alcohol, glycerine, and 

 various poisons, may distinctly accelerate streaming, for a time at least, 

 even when all shock-effect is avoided by gradual change. The effect of 

 shock is commonly to produce a retardation or stoppage followed by a 

 subsequent acceleration, but all these responses are manifestations of 

 irritability and bear no relation to the changes of viscosity directly due 

 to the presence of the exciting substance. Strong solutions of neutral 

 substances, however, retard streaming largely owing to the rise of viscosity 

 consequent on the withdrawal of water. 



Transitory chloroforming 6 , or treatment with solutions of poisonous 

 or nutrient substances, may awaken streaming in quiescent cells, such as 

 those of Vallisneria, and similarly all substances which act as chemical 

 stimuli to the tentacles of Drosera also act as excitants to streaming in the 

 responsive cells of this plant. Anaesthetics, such as ether, chloroform, and 

 chloral hydrate, as well as such alkaloids as caffein, antipyrin, muscarin, 

 atropin, eserin, veratrin, and curare readily retard and ultimately stop 

 streaming and locomotory movement even when dilute. Muscarin, atropin, 

 and veratrin, however, which are deadly poisons to higher animals, exercise 

 relatively little effect upon plants 7 , and may indeed be used as a food-material 

 by such Fungi as Penicillium*. Anaesthetics appear commonly to stop 



1 Demoor, Contrib. a 1'etude de la Physiol. de la cellule, 1894, p. 35. 



2 Samassa, 1. c., p. 2 ; Kauffman, Einwirkung der Anaesthetica auf Pflanzen, 1899, p. 16. 

 8 Kiihne, 1. c., p. 92 : cf. Ritter, 1. c., p. 358. 



* Ewart, 1. c., p. 350. Ritter (1. c., p. 350) found that after the prolonged absence of oxygen 

 this gas was immediately evolved on exposure to weak light, whereas the presence of absorbent 

 substances should retard its appearance for some time. Pringsheim (Sitzungsb. d, Berl. Akad., 1887, 

 p. 769) did actually find that Chara became incapable of evolving oxygen after remaining for a long 

 time in darkness, but this was due to the induction of a condition of assimilatory inhibition in the 

 chloroplastids. Cf. Ewart, Journ. Linn. Soc., 1896, p. 418. 



5 Demoor, 1. c., p. 72 ; Lopriore, 1. c., 1895, pp. 573, 621 ; Klemm, Jahrb. f. wiss. Bot., 1895, 

 Bd. xxvill, p. 680; Samassa, 1. c., p. 2; Kiihne, 1. c., 1898, p. 36; Farmer u. Waller, Bot. 

 Centralbl., 1898, Bd. LXXIV, p. 377; Kauffmann, 1. c., p. 10; Josing, 1. c., p. 223. For the detailed 

 action of various chemicals see Ewart, Protoplasmic Streaming in Plants, 1903, p. 76. 



6 Hauptfleisch, Jahrb. f. wiss. Bot., 1892, Bd. XXIV, p. 220. 



7 Ewart, 1. c., p. 86. 



8 Ewart, 1. c., p. 81. 



