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and Potamogeton that the assimilation may be stopped when a suitable dose of 

 ethei' is added to the water. The plant being removed to normal surroundings 

 the assimilation is regained [Bernard p. 278]. The same phenomenon was noted 

 by Bonnier & Mangin [Bonnier & Mangin p. 14] and Jumelle, who experimented 

 with shoots ofQuercns, Carpinus and Fagus, with Pteris and with Solanum [Jumelle 

 1890, p. 417 seq.], also by Pfeffer [Pfeffer 1896] and by Octave Treboux, who used 

 Elodea for his experiments [Treboux p. 49 seq.]. Ewart experimenting with mosses 

 found the same result; if the mosses had been exposed to ether for a length of 

 time, 2 or 3 days might elapse, before the normal degree of the assimilation had 

 been regained. Young cells showed a greater resistance to ether than the older 

 ones [Ewart 1895 p. 408— 410]. Contrary to this Frank Schwartz, who examined 

 Elodea and Ceratophyllum, noted that the assimilation arrested b}' ether could not 

 be regained, when the plants where transferred to normal conditions. These 

 results of his experiments may be owing to the circumstance that he used too 

 large doses (he placed a sponge dipped in ether in the water in which the plants 

 were growing) [Schwarz 1881, p. 97 — 104]. Pringsheim noted the same phenomenon 

 in Chara [Pringsheim 1887, p. 776]. W. Kegel experimented with Elodea canadensis. 

 He stated that the assimilation is always accelerated in water containing 7—6 per 

 cent ether, while this process immediately or shortly after is arrested, when smaller 

 doses are used. When the plants had been transferred to clean water the intensity 

 of the assimilation soon became normal, the exposition to ether having not been 

 of too long duration [Kegel 1905]. Schroeder objects against these theories that the 

 accelerated evolution of air-bubbles caused directly by a 6 to 7 per cent water 

 solution of ether does not depend upon accelerated assimilation but is the effect 

 of an entirely physical phenomenon, the ether entering the intercellular spaces and 

 driving away the air. Scliroeder's objection seems to be reasonable, for if the 

 effect of etherization on assimilation coincided with the theory of Kegel, it would 

 be entirely unlike the effect of ether in the other processes [Schroeder 1908 p. 168]. 

 Francis Darwin has proved that the stomata close in an atmosphere of ether, a 

 phenomenon which probably aids the above mentioned arresting of the assimila- 

 tion; in normal surroundings the stomata open again [Darwin 1898 p. 571]. As 

 ether and chloroform arrest the COo-assimilation, it is obvious that the above 

 mentioned substances also affect the formation of chloroplastids; the case has been 

 investigated bj' Teodoresco and Conpin ; they used for their researches Triticum, 

 Vicia, Fagopyrum and Lupinus. Their experiments proved that ether and chloro- 

 form arrest the formation of chlorophyll bodies, the formation being arrested 

 according to the increased doses and increased length of exposition. When the 

 doses reach a certain degree, the formation is entirely stopped [Teodoresco and 

 Conpin p. 884—887]. Later on Kauffmann reached the same result [Kauffmann 

 1899 p. 53]. 



Summing up the above mentioned results we may take for granted that the 

 assimilation may be entirely arrested for a short time, when suitable doses are 



29* 



