Secure a leaf from a plant which has been in the darkness for 

 about two days. Dissolve the chlorophyll as before, and attempt 

 to stain this leaf with iodine. No purplish-brown color is pro- 

 duced. A leaf kept in darkness contains no starch. 



This demonstration may be made much more instructive i n 

 another way. Secure a plant which has been kept in darkness 

 for twenty-four hours or more. Split a small cork and pin the two 

 halves on opposite sides of one of the leaves, as shown in Fig. i . 

 Place the plant in the sunlight again. After a morning of bright 

 sunshine dissolve the chlorophyll in this leaf with alcohol, as 

 before ; then stain the leaf with the iodine. Notice that the leaf 

 is stained deeply in all parts except in that part over which the 

 cork was placed, as in Fig. 2. There is no starch in this area. 

 These experiments also make it evident that the starch man- 

 ufactured in the leaf maybe entirely removed during darkness. 



9. Plants or parts of plants which have developed no chlofvphyll 

 canforni no starch. — Secure a variegated leaf of coleus, ribbon 

 grass, geranium, or of any plant showing both white and green 

 areas. On a day of bright sunshine test one of these leaves by 

 the alcohol and iodine method for the presence of starch. 

 Observe that the parts devoid of green color have formed no 

 starch. However, after starch has once been formed in the 

 leaves, it may then be changed and removed to be again formed 

 as starch in other parts of the living tissues. 



10, Starch is in the form of ijisoluble granules. Whenever the 

 niaterial is carried frofu one part of the plant to a7iother for purposes 

 of growth or storage, it is changed to sngar before it can be trans- 

 ported. When this starch}- material is transferred from place to 

 place, it is made soluble, changed into sugar, by the action of a 

 ferment. This is a process of digestion. It is much like the 

 change of starchy foods to sugary foods by the saliva of the mouth. 



After being changed to the soluble form, this material is ready 

 to be used in growth, either in the leaf, in the stem, or in the 

 roots. With other more complex products it is then distributed 

 throughout all of the growing parts of the plant ; and when 

 passing down to the root it passes more readil}' through the 

 inner bark, in plants which have a definite bark. This gradual 

 downward diffusion of materials suitable for growth through the 



