82 NATURE TEACHING. 



expense of the food reserves stored away iij 

 the tuber or seed. It is only later, when the 

 new shoot has formed its own green leaves, 

 that it can do anything at all towards making 

 fresh supplies of food for itself. 



3. It has already been stated, and will 

 later be experimentally proved, that assimila- 

 tion, resulting in the formation of starch, can 

 only go on in the green parts of plants, and 

 only there when they are exposed to sunlight. 

 The question naturally arises then : How do 

 we find starch in tubers, seeds, or other non- 

 green and even underground parts of plants ? 

 The answer to this, too, will be supplied by 

 means of simple experiments. If a growing- 

 plant is left exposed to a good light from early 

 morning to afternoon and its leaves tested 

 then, they will be found to be loaded with 

 starch. But, place this same plant in darkness 

 for twelve hours or more, and its leaves will 

 be found to be almost emptied of starch. As 

 a matter of fact the starch formed in them in 

 the sunlight has been carried away by the 

 plant from the leaves in which it was made, 

 and either used up in growth or stored up in 

 some other part as a reserve of food. 



4. A plant requires for its complete nour- 

 ishment other food substances besides carbon 



