128 WATER-ABSORPTION AND TRANSPIRATION. 



13. Describe simple experiments which show through what part of 

 the stem water ascends. How would you arrange an experiment to 

 show the relation between the volumes of water absorbed and given off? 



14. Describe some ways by which you could demonstrate that leaves 

 give off water vapour. How do external conditions affect the magni- 

 tude of this process ? What is the significance of it in the life of the 

 plant ? 



15. Give an account of the process of transpiration. By what means 

 does the plant regulate its transpiration ? 



16. If on a warm sunny day a plant growing in a pot had become 

 limp and "wilted," how could you restore it to its normal condition 

 without watering it in any way ? 



17. Why does the inside of a Cabbage consist of lighter-coloured, 

 thicker, and more succulent leaves than the outside ? 



18. Explain why it is that plants droop on a hot day, and recover 

 their freshness in the evening. 



19. Describe experiments you have made on Transpiration, and 

 explain how the rate of transpiration is affected under different 

 conditions. 



20. How does a plant dispose of the water which it absorbs from the 

 soil ? Describe any arrangements with which you are acquainted for 

 regulating the quantity of water in a plant. 



21. Indicate the probable presence or absence of Respiration, Trans- 

 piration, and Photosynthesis in the green and white parts, respectively, 

 of the variegated leaf of a plant under normal conditions, (a) in the 

 daytime, (6) at night. Give brief reasons for your answers. 



22. Mention all the gases given off by a foliage-leaf under different 

 conditions. Explain briefly how you would demonstrate by experiment 

 the evolution of these gases ; and give an account of the processes 

 leading up to their formation. 



23. Explain, so far as you can, exactly how plants grown in pots in 

 sitting-rooms are affected by draughts, by burning gas, by one-sided 

 illumination, by the different aspects of windows, by a dry atmosphere, 

 by injudicious watering, and by other conditions to which they are 

 likely to be exposed. 



24. Describe carefully, with illustrative diagrams, two methods of 

 finding out which side of an ordinary dorsiventral foliage-leaf gives off 

 more water vapour. To what structural features and to what biological 

 advantage is the observed difference related ? 



25. What would be the result of smearing both surfaces of all the 

 leaves of a plant with vaseline or other greasy substance ? How would 

 you determine experimentally the effects so brought about ? 



26. What are the " veins " of a leaf ? What are their uses ? How 

 would you show, by experiment, the correctness of your statements ? 



