PLANT-LIFEASSIMILATION. 221 



is retained and unites with the ascending 

 water to form the so-called carbohydrates (as 

 sugar, starch, and also the proteids). These 

 are known as organic substances, since they 

 are products of life, of Nature's own labora- 

 tory. Also they are the food-stuff of the 

 Plant manufactured by itself out of the afore- 

 said raw materials. But this cooked food is 

 still to be digested and vitalized into what is 

 called vegetal protoplasm, which is to be car- 

 ried to and incorporated with every living 

 portion of the Plant. Such is the general out- 

 come of the work of Alimentation, which may 

 be taken as the first stage of the total process 

 of Assimilation : the given outer elements are 

 transformed into a living food-supply, and 

 thus assimilated to the living organism, 

 though not yet organized into it actively. 



The aliment of the Plant being thus ob- 

 tained, it must next be distributed through- 

 out the organism. This is done by means of 

 a distributing circulation, which has a num- 

 ber of streams running through the entire 

 vegetal body on different errands. 



2. Distribution. In the Plant there is no 

 central heart with its pumping power of cir- 

 culating the blood; still there are in it various 

 kinds of movement of various fluids. The as- 

 cent of the sap is probably best known; but 

 botanists also speak of the circulation of the 



