126 



THE AMEKICAN MONTHLY 



[July, 



hairs and the tentacular hairs of 

 the insectivorous plants. Such hairs 

 are primarily absorbing organs, tak- 

 ing up for the use of the plant not 

 only nitrogen and nitrogenous com- 

 pounds, but probably also oxygen. 



It is generally agreed that there are 

 but two principal physiological pro- 

 cesses going on in the plant, namely, 

 assimilation (the elaboration of or- 

 ganic compounds out of inorganic), 

 and metastasis (the transmutation of 

 one organic compound into another). 

 Assimilation is that process by which 

 carbon-dioxide and water are decom- 

 posed and their elements formed in- 

 to what are known as the carbo-hy- 

 drates, of which starch is the most 

 important. In this process oxygen 

 is liberated and exhaled. Assimilation 

 can take place only in the chloro- 

 phyll-bearing cells, in the presence of 

 light and a certain degree of heat. 

 The materials produced by this pro- 

 cess are the only materials which are 

 suitable for use as food for the pro- 

 toplasmic basis of life in the plant, 

 which is the seat of growth and re- 

 production. The process by which 

 these carbo-hydrates are appropri- 

 ated to the specific purposes of the 

 plant, are transported from one part 

 to another, and transmuted into ac- 

 tive, living, propagating and then per- 

 manent vegetable tissue, is what is 

 called metastasis. Inorganic sub- 

 stances cannot be directly appropri- 

 ated by the protoplasm of the plant, 

 except perhaps to a very limited ex- 

 tent in some special cases. Assimila- 

 tion, therefore, is a somewhat doubt- 

 ful name for a preparatory process, of 

 which metastasis is the ultimate object. 

 Metastasis is, therefore, really the as- 

 similative process, and corresponds 

 to the process to which the name 

 assimilation is given in animal physi- 

 ology ; while assimilation, so-called 

 in vegetable physiology, is more anal- 

 agous to the preparatory process of 

 digestion in animals. There is greater 

 analogy between the vegetal pro- 

 cess of metastasis and the animal 

 process of assimilation from the fact 



that oxidation, by some sort of res- 

 piration or absorption from without, 

 is an essential part of each. 



It has already been stated that 

 what is termed assimilation, takes 

 place only in the chlorophyll-bearing 

 cells in the presence of light and heat. 

 Therefore, fungi, parasitical plants 

 and, generally, plants which are des- 

 titute of chlorophyll, are unable to 

 perform the assimilative process. 

 They must therefore obtain for their 

 food ready-made, organic compounds, 

 and are, in this respect, like animals. 



Unlike the process of assimilation, 

 metastasis takes place in cells which 

 do not bear chlorophyll, or else in the 

 chlorophyll-cells in the absence of 

 light ; and while the assimilative pro- 

 cess is promoted by light and warmth, 

 the metastatic process is promoted 

 by darkness and probably by a 

 lower temperature. What aids the 

 one process retards the other ; 

 so that the assimilative process is 

 active in the day-time when the met- 

 astatic process is checked, and the 

 latter process is active at night when 

 assimilation is checked. Day-time is 

 therefore the period of preparation, 

 and night time the period of 

 growth in plants. In the day-time 

 they take up and decompose the 

 compounds from which the carbo- 

 hydrates are formed, at the same 

 time exhaling oxygen, and at 

 night they inspire oxygen for the pur- 

 poses of internal change and growth, 

 at that time exhaling the products 

 of oxidation, which consist mostly 

 of carbon-dioxide. Now this fact is 

 to be particularly noted, that the pro- 

 toplasm of the plant is its life-bearing 

 element, and that the process of meta- 

 stasis is a process directly connected 

 with the preservation, augmentation, 

 modification and reproduction of this 

 life-bearing element ; while the pro- 

 cess called assimilation is almost 

 purely chemical, and has for its re- 

 sult merely the production of appro- 

 priate material for the metastatic 

 process. 



It has been shown that the rotation 



