THE LEAVES 63 



(6) Breathing-pores are usually found on the under side of 

 leaves ; but in water plants that rest on the surface of the water 

 they are found only on the upper side. Why ? 



(7) Why are there breathing-pores on both sides of a gum tree 

 leaf? 



(8) Breathing-pores are not generally found on stems and spines. 

 The gorse is an exception. Why ? 



(9) Where would you expect to find the breathing-pores in a 

 prickly pear plant? In a cactus ? 



(10) Cactuses and other desert plants have few breathing-pores. 

 Why is this ? 



(11) A lilac leaf has 160,000 breathing-pores for every square 

 inch. A mistletoe leaf has only 200 per square inch. Why has 

 the mistletoe so few ? 



(12) Experiment to shew that air escapes through the breathing- 

 pores of a leaf. Get a leaf of the primrose, or still better, of the 

 Chinese primrose, with a clean-cut stalk. Place the stalk in the 

 mouth and the blade in water. Blow into the stalk, and air will 

 pass through the leaf into the water. 



Composition exercise : — Tell the story of how earth, air, 

 plant, and sun all work to make you bread. Shew how the cow 

 must help before you can get butter with the bread. 



Drawing exercise : — Draw from fig. 35 the inside of a leaf. 

 Colour the cells that contain the living green stuff. 



XI.— THE LEAVES.— Paet III. 



Some Experiments. 



1. We saw that the living green stuff in the leaf 

 makes starch, sugar and other materials that the plant 

 needs. That the plant makes sugar you know well ; 

 for you taste it every time you eat a cherry or a bunch 

 of grapes, or bite the honey-tube of the nasturtium. 

 Starch also you know well ; for the Indian corn-flour 

 used for puddings is almost pure starch. Potatoes, 

 too, are made almost entirely of starch. Some of the 



