I I O PLANT BIOL OGY 



the carbon dioxid of the air. In some small groups of 

 bacteria a process of organic synthesis has been shown to 

 take place. 



Epiphytes. — To be distinguished from the dependent 

 plants are those that grow on other plants without taking 

 food from them. These are green-leaved plants whose 

 roots burrow in the bark of the host plant and perhaps 

 derive some food from it, but which subsist chiefly on 

 materials that they secure from air dust, rain water, and 

 the air. These plants are epiphytes (meaning "upon 

 plants") or air plants. 



Epiphytes abound in the tropics. Certain orchids are 

 among the best known examples (Fig. 37). The Spanish 

 moss or tillandsia of the South is another. Mosses and 

 lichens that grow on trees and fences may also be called 

 epiphytes. In the struggle for existence, the plants 

 probably liave been driven to these special places in which 

 to find opportunity to grow. Plants grow where they 

 must, not where they will. 



Suggestions. — 114. Is a puffball a plant ? Why do you 

 think so? 115. Are mushrooms ever cultivated, and where 

 and how? 116. In what locations are mushrooms and toadstools 

 usually found? (There is really no distinction between mush- 

 rooms and toadstools. They are all mushrooms.) 117. What 

 kinds of mildew, blight, and rust do you know? 118. How do 

 farmers overcome potato blight? Apple scab? Or any other 

 fungous "plant disease"? 119. How do these things injure 

 plants? 120. What is a plant disease? 121. The pupil should 

 know that every spot or injury on a leaf or stem is caused by 

 something, — as an insect, a fungus, wind, hail, drought, or other 

 agency. How many uninjured or perfect leaves are there on 

 the plant growing nearest the schoolhouse steps? 122. Give 

 formula for Bordeaux mixture and tell how and for what it is used. 



