128 



THE PRINCIPLES OP AGRICULTURE 



one of the peculiarities of green plants; and animals depend on 

 plants for the preliminary preparation of these necessary com- 

 pounds. 



198a. The word assimilation is sometimes used in this restricted 



sense in plants, as defined in 

 198. In general speech it 

 means the appropriation of 

 prepared or digested food, as 

 the assimilation of the food 

 by the blood, or protoplasm. 



1966. Chlorophyll is the 

 green coloring matter of 

 plants. It looks to be in the 

 form of minute grains. Most 

 of the cells in Fig. 38 contain 

 chlorophyll grains. 



198c. Plant-food, in the 

 sense in which the term is 

 here used, is a product of pho- 

 tosynthesis,— sugar, starch or 

 some similar material. In 

 common speech the term food 

 is used to designate anj'^ ma- 

 terial taken in and ultimately 

 used by the plant, as nitrates, 

 potash, water; and a general 

 use of the term is so well 

 established that it cannot be 

 overthrown. 



198(7. For further light on 

 assimilation, compare Arthur 

 and MacDougal, "Living 

 Plants and Their Properties," pp. 145-152. 



199a. Place under a funnel in a deep beaker, containing 

 fresh spring or stream water, growing bits of water-weed 

 (Elodea Canadensis), and invert over the end of the funnel a test- 

 tube filled with water, as in Fig. 41 . In the sunlight bubbles of 



Fig. 41. Experiment to show the giving 

 off of oxygen. 



