764 THE POPULAR SCIENCE MONTHLY. 



be quite possible. But it is also possible that the difference may be 

 a physical one. To produce the colloid state from the crystalloid is 

 by no means beyond the power of science. We qualify our previous 

 statement, then, only so far as to say that when the chemist produces 

 a body in the colloidal form, having the identical constitution of pro- 

 toplasm, there is every reason to believe that it will have the proper- 

 ties of protoplasm. 



The important question now arises whether, since the protoplasm 

 of animals is identical with that of vegetables, and the latter is the 

 food of the former, any protoplasm whatever is vitalized by the animal 

 as such. That this identity exists would seem satisfactorily estab- 

 lished. Though the protoplasm of vegetables is inclosed within a 

 cellulose bag, it is only a closely imprisoned rhizopod. In the Nitella, 

 it shows all its characteristic irritability, and from Vaucheria it escapes 

 to exhibit all its amoeboid movements. Spores swim about by cilia or 

 flagella, and the cell-division of the one kingdom is the same as that 

 of the other. In plants, however, protoplasm seems to be associated 

 with chlorophyl, whose function was for a long time supposed to be 

 to decompose carbon dioxide under the influence of sunlight. But 

 Draper in 1843 showed that this decomposition took place before the 

 chlorophyl was formed. Recent researches have shown that the func- 

 tion of chlorophyl is wholly protective. The assimilative power of 

 the protoplasm reaches its maximum in the orange and yellow rays. 

 Now, Bert has shown that the absorption band in the chlorophyl spec- 

 trum is in the exact position of this maximum. Hence, Gautier be- 

 lieves that this substance acts as a regulator of plant respiration, the 

 greater or less amount of luminous energy thus absorbed and trans- 

 formed being utilized by the protoplasm and stored up. Growth and 

 cell-division, however, are independent of orange light and hence of 

 chlorophyl. In the higher plants these functions are performed by a 

 separate and deep-lying set of cells. But, in the lower, the same cell 

 discharges both functions, assimilation going on in it during the day, 

 and growth chiefly at night. Sachs had already proved that the maxi- 

 mum growth of plants takes place just before daylight, and the mini- 

 mum in the afternoon. This retarding action of sunlight upon growth 

 is as curious as it is unexpected. It now appears that in orange light 

 plants assimilate absorb carbon dioxide and evolve oxygen but do 

 not grow are not heliotropic ; while in blue light they are strongly 

 heliotropic, but do not give off oxygen. Chlorophyl, however, is not 

 confined to vegetables ; infusoria, hydras, and certain planarian worms 

 are green from the presence of this substance, and Geddes has shown 

 that such animals placed in the sunlight give off a gas which is more 

 than half oxygen. These cells, moreover, contain starch-granules. 



A still more striking evidence of this intimate relationship has 

 been developed by Darwin, in his researches upon insectivorous 

 plants. Not only do these plants possess a mechanism for capturing 



