WATER-ABSORPTION AND TRANSPIRATION. 129 



27. If you take two similar open vessels full of water, and place a 

 leafy shoot with its cut end in one, from which will the water disappear 

 more rapidly ? Explain, as fully as you can, the reason for the ob- 

 served result, and the nature of the processes involved. 



28. Explain why it is that a shoot which is cut off from a plant 

 begins to wither and droop. How can this be prevented ? How can a 

 flagging branch be revived ? 



29. What purposes are served by the process of transpiration ? 

 Under what conditions is this process accelerated and retarded ? 



30. A green plant is in ordinary life continually giving off water. 

 Explain how this is effected, and what is its purpose. How is the 

 process affected by changes in the air and in the soil ? 



31. How would you prove (1) the nature of the gas given off by a 

 green plant in sunlight, (2) the nature of the gas given off by a green 

 plant in the dark, (3) the nature of the liquid deposited on the inside 

 of a bell-jar covering a growing plant ? Give an account of the pro- 

 cesses leading to the formation of the liquid. 



32. Trace the path followed by a particle of water, from its entrance 

 into the root to its exit, as vapour, from the leaf. 



33. On what part of the root are root-hairs found ? Under what con- 

 ditions are the most conspicuous root-hairs produced ? What is the 

 function of root-hairs ? How can you imitate the process involved by 

 a mechanical contrivance ? 



34. Show how some of the commoner operations of gardening, such as 

 digging, manuring, raking, transplanting and watering, may be con- 

 ducted, so as best to minister to the chemical and physical conditions 

 of plant life. 



35. How would you examine a handful of soil to see if it contained 

 any soluble salts ? How could you prove that nitrates (of soda, 

 potash, or lime) are present in a fertile soil? 



36. Describe carefully and illustrate by diagrams the details of the 

 procedure you would follow in order to find out the differences pro- 

 duced in the roots of seedlings by growing (a) in ordinary soil, (b) in 

 water-culture solution, (c) in damp air. What differences would you 

 observe between the roots in the three cases, and how are they related 

 to the different conditions of life ? What would be the ultimate fate 

 of the three sets of seedlings ? 



37. Explain why it is injurious to plants grown in pots to be too 

 frequently and too abundantly watered. 



38. Can you measure the moisture present (a) in the soil, (b) in the 

 air? State exactly what effect each has on a growing plant, and how 

 you would demonstrate the effect in each case. 



39. What are root-hairs ? Where do they occur, and what is their 

 function ? 



3. B. 9 



