PHYSIOLOGY OF GROWTH AND MOVEMENT 163 



QUESTIONS ON CHAPTER XII. 



(1) Define the term growth. What conditions are necessary for 

 growth ? 



(2) Why does Rhubarb grow faster in the dark than in the light ? 



(3) Give an account of an experiment which proves that plants 

 grow faster in the dark than in the light. 



(4) Explain, and illustrate by an experiment what is meant by " a 

 grand period of growth " in the life of a plant. 



(5) The protoplasm is said to possess the property of irritability. 

 Explain this. 



(6) Why do the stems and leaves of window plants take up a definite 

 position with regard to the light ? 



(7) Explain the term heliotropism. Aerial stems are said to be 

 positively heliotropic and roots negatively heliotropic. Explain this. 



(8) A plant is covered with a blue glass. How will its method of 

 growth differ from one grown under red glass ? 



(9) Explain why it is that, when a seed germinates, the stem grows 

 upwards and the root downwards. (1889 and 1897.) 



(10) Describe, and briefly explain, the influence of light upon the 

 direction of growth of stems and of roots. (1891.) 



( 1 1 ) What is the effect of light upon the direction of growth of stems 

 and leaves? (1896.) 



(12) Most flowers are open in the light and closed during darkness. 

 Explain how this change is produced, and of what service it is to the 

 flower. 



M 2 



