Teachers' Leaflet. 523 



in the green parts of the plant can take on changes and travel to all 

 parts of its body and change back to starch grains and rest there until 

 the starch is needed to enter the growth of some of the many parts, such 

 as new twigs, new roots, flowers or fruits and particularly seeds. 



All thrifty trees — fruit trees, we will say — may have more starch 

 than is needed for the time being and it is held for future use, much as 

 a prudent man will put money into the savings bank for a time of need. 



If you wish to see with your own eyes the grains of starch which 

 the plant has stored away for future use, you can do so by using what 

 is called the iodine test. It is a simple experiment and the teacher may 

 be kind enough to help the pupil in doing it: Into a small bottle put a 

 few drops of tincture of iodine and add fifteen times as much water as 

 the quantity of the tincture. Keep the bottle corked when not in use. 

 On a thin slice of potato put a small drop of diluted iodine, no more 

 than will stick to the tip of a tooth pick or broom splint. Instantly 

 you will see a purple or purplish-brown stain. Under a lens, even of 

 very low power, the stain shows as a collection of purple specks. Those 

 are starch grains which the iodine has colored. The starch grains 

 in a potato are important factors that make it so valuable as a food. 



LESSON XC. 



Purpose. — To show that plant-food is stored in the branches of 

 trees in winter. 



Experiment. — In March have the pupils cut twigs from willows, 

 lilac or apple and place them in a bottle of water and let them watch 

 the leaves develop. 



The willows are among the first shrubs to awaken in the spring. 

 Cut some long twigs and put them in a bottle of water. After a short 

 time the buds will enlarge and then the leaves will put out and a shoot 

 will show a little growth. All this growth requires substance, which 

 comes from the starch that was stored in the twig the season before. 

 The water in the bottle enables the starch to take a form so as to be 

 available for making growth, but water alone cannot give that growth. 



LESSON XCI. 



Purpose. — To cause the pupils to think why fodder and grass should 

 be cut before ripe. 



Observation lesson. — In haying time let the pupils in rural districts 

 find out by questioning their fathers the fact that hay to be good should 

 be cut before it is entirely ripe. 



