308 THE PRINCIPLES OF AGRICULTURE 



wants a completer account of these matters he 

 should consult botanical text- books. It will be 

 noticed that the chapter divides into four co- 

 ordinate heads: (1) what the plant activities are; 

 (2) the factors or agencies of growth; (3) the 

 processes of growth; (4) irritability, or move- 

 ment in plants. 



What is meant by the phrase that the plant is a "dependent 

 structure?" With what must the plant be supplied in order that 

 it shall live and grow? What is meant by the sensitiveness or 

 irritability of a plant? 



Upon what does the stiffness or rigidness of a succulent plant 

 depend? Why does such a shoot wilt when it is severed from the 

 plant? What is meant by the turgidity of the cells? How does 

 the soil- water pass from cell to cell? Explain or illustrate tur- 

 gidity (184a). What are root-hairs, and what is their office? 

 How is it that these root-hairs absorb the soil water? What does 

 the soil-water contain? The pupil should actually see and examine 

 root-hairs. Compare 185& and figures 35-37. How much water 

 do plants contain? Do plants absorb more water than they need 

 for purposes of food? If so, what becomes of the surplus? What 

 are stomata? What is their action? Illustrate transpiration (see 

 figures 40 and 10). What is root pressure? Through what part 

 of the plant does the soil water ascend? How may the path of 

 ascent be traced (1896)? 



What is absorbed with the soil-water? To what part of the 

 plant does this soil-water, with its contents, go? Does the plant 

 absorb only those substances that are use in building up its tissue? 

 How may soil substances that are not in solution be brought into 

 that condition? Name some of the leading substances that are 

 brought in with the soil -water, particularly those that are of 

 primary interest to the farmer? What is meant by the "ash"? 

 What does the ash contain? Do all the ash ingredients come from 

 the soil? Do any of the non-ash ingredients come from the 

 soil? 



