PROTOPLASMIC STREAMING 289 



maintained between the total energy of respiration and that used in streaming. 

 In fact, streaming is usually more rapid, or at least as rapid in the narrow cells along 

 the midrib of Elodea, as in the broader parenchyma cells. 



Historical 1 . Streaming movements were first observed in the cells of plants by 

 Corti in i774 2 . These observations were amplified and extended by Fontana, Tre- 

 viranus 3 , Amici 4 , Slack 5 , Meyen 6 , Dutrochet 7 , Schleiden 8 , and Hassal 9 , but it was 

 not until Von Mohl had established the fact that the protoplasm was the essential living 

 substance of the plant-cell that Schacht 10 showed the seat of active movement to be 

 in the protoplasm, and concluded that streaming was merely an outward and visible 

 sign of the activity of the latter. 



Velten assumed that streaming was a general and normal phenomenon, whereas 

 Frank, Keller, and Hauptfleisch have shown that in many cases it is only awakened 

 by external stimulation n . De Vries and also Janse considered that streaming was 

 of primary importance for the rapid transport of food-materials, and the same con- 

 clusion has been made by Hermann 12 . It is, however, only in very large cells that 

 this applies, for in ordinary plant-cells transference by diffusion is more rapid than 

 by streaming movement 13 . 



Theories of Streaming. Heidenhain and Ku'hne 14 considered that waves of con- 

 traction passed round the cell, producing streaming in the same way as when the 

 finger is drawn round an india-rubber tube filled with water. A similar explanation 

 was originally put forward by Corti 15 , but de Bary and others have shown that the 

 contour of the protoplasm towards the cell-sap does not alter in the way required by 

 the theory 16 . In any case, the streaming in dermatoplasts can hardly be produced in 

 the same way as in gymnoplasts, in which it is passively produced by the contractile 

 activity of the peripheral layers. Yet another type of passive streaming has been 

 shown by Arthur 17 to exist in the mycelial filaments of many Fungi when local 

 variations of osmotic pressure coupled with the excretion or absorption of water 



1 See Ewart, Protoplasmic Streaming in Plants, 1903, p. i seq. 



2 Osservazioni microscopiche sulla Tremella e sulla circolazione del fluido in una pianta 

 acquaiola, Lucca, 17/4, p. 127. 



3 Physiologia, 1807. 



4 Mem. della Soc. Ital. delle Scienze in Modena, 1818, T. xvm, p. 182. 



5 Ann. sci. nat., 1834, 2& s ^r., T. I, pp. 193, 271. 



Id., 1835, 2" ser., T. iv, p. 257. 7 Id., 1838, 2 e ser., T. IX, pp. 5, 65. 



8 Principles of Botany (Eng. Trans.), 1849, p. 92. 



9 British Freshwater Algae, Vol. I, p. 85. 10 Die Pflanzenzelle, 1852, p. 340. 



11 Velten, Bot. Ztg., 1872, p. 147 ; Flora, 1873, p. 82 ; Frank, Pringsh. Jahrb., 1872, Bd. vm, 

 p. 220 ; Keller, Ueber Protoplasmastromung im Pflanzenreich, 1890, pp. 12, 40 ; Hauptfleisch, Jahrb. 

 f. wiss. Bot., 1892, Bd. xxiv. 



12 De Vries, Bot. Ztg., 1885, Nos. i and 2, p. i ; Janse, Jahrb. f. wiss. Bot., 1890, Bd. xxi, 



p. 163. 



13 Ewart, The Ascent of Water in Trees, Phil. Trans., 1905, p. 80. 



14 Heidenhain, Studien d. physiol. Inst. in Breslau, 1863, Bd. II, p. 60; Kiihne, Unters. tiber d. 

 Protoplasma, 1864, pp. 73, 91. 



15 Quoted by Goppert and Cohn, Bot. Ztg., 1849, p. 666. 



16 De Bary, Flora, 1862, p. 250; Schultze, Das Protoplasma d. Rhizopoden u. d. Pflanzenzellen, 

 1863, p. 40; Nageli und Schwendener, Mikroskop, 1877, 2. Aufl., p. 389. 



17 Arthur, Annals of Botany, 1897, Vol. XI, p. 491. 



PFEFFER. Ill U 



