AN INTRODUCTION TO FLAX1 BIQL'IG*- 101 



Most plants without chlorophyll are saprophytes ; but some 

 of them absorb the necessary food from living plants or 

 animals, and such plants are called parasites (e.g., dodder, 

 and mistletoe to some extent). 



99. Food of Plants with Chlorophyll. Such plants have 

 in their bodies at least the same ten essential elements ( 96) 

 as plants without chlorophyll. Nine of these elements (all 

 except carbon, and some oxygen) are obtained from the soil, 

 the hydrogen and oxygen in the form of water (H 2 0) and 

 the other seven in solution in water absorbed by the roots. 

 The one fundamental difference between the nutrition of 

 plants with and without chlorophyll is that the chlorophyll is 

 a special substance with the aid of which the protoplasm of 

 leaf-cells is able under the action of light to make the car- 

 bohydrate food needed by the plant, while plants without 

 chlorophyll must absorb, by their roots, such food from 

 the decaying bodies of other plants or animals. 



Cells containing chlorophyll are able in light to make car- 

 bohydrate food in the form of starch or sugar, obtaining the 

 necessary elements from water, from the soil, and from carbon 

 dioxide from the air.* This production of sugar and starch 

 takes place chiefly in the leaves. Probably sugar is first 

 formed and then changed into starch ; but since starch is 

 usually demonstrable in green leaves exposed to light, we 

 shall give special attention to its formation. However, it 

 makes no difference to the plant whether sugar or starch 

 is formed in the leaves, for they are of equal value as food 

 for all plant cells. 



The stomata allow watery vapor to escape, in transpiration, 

 and they are also important in allowing air with carbon di- 



* The atmosphere contains on the average about three parts of carbon 

 dioxide in 10,000 of air, measured by volume ; and yet from this exceedingly 

 small amount of carbon dioxide the green plants get the necessary carbon for 

 making all carbohydrates, which compose a large part of the solid matter 

 of plants. 



