118 XATUBE-STUDY LESSONS. 



{b) What do you observe ? 



{c) Where has the moisture come from ? 



14. Where does the leaf on the stem obtain water? 



15. Observe the effect on the leaves of withholding 

 water from a potted plant. 



16. From the above experiment, account for the wither- 

 ing of the leaves of the potted plant. 



This process of evaporation of water from the leaf is called transpiration. 

 The water or vapor passes off from the leaf through minute openings, 

 or stomata ; these are found on both surfaces of the leaf, but are usually 

 most numerous on the under side. 



17. (fl) Set in a window, where there is plenty of 



direct sunlight, a tumbler containing water 



and having the blade of a vigorous leaf 



immersed in it. 

 ip) After an hour or so examine the leaf What do 



you observe rising from and on the surface 



of the leaf? 

 {c) Now, set the tumbler with the leaf in darkness 



and after an hour examine it again. 



(d) Compare this observation with that made 



when the glass and leaf were in sunlight. 



(e) Again, place the glass with the leaf in direct 



sunlight and after some little time observe 



what takes place. 



(/) From these observations infer the condition 



for this activity in the leaf. 



These bubbles found on and rising from the leaf are mostly bubbles of 

 oxygen. The setting free of this gas from and by the leaf is an indication 

 of work being performed by the leaf in the process of digesting its food. 



18. {a) Have a couple of fruit-jars with closely-fitting 



tops. Burn a candle in one until it will bum 

 no longer. Relight it and again place it in 

 the jar. 

 ip) What is the result? 



