130 



THE PRINCIPLES OF AGRICULTURE 



Fig. 44. 



Marking the 



root. 



organ, spread a drop of tincture of iodine on the cut surface, 

 and the blue or violet color indicates the presence of starch. 

 Test the laundry starch. 



2036. To determine that starch is formed 

 only in the green parts of leaves, secure a 

 leaf variegated with white, like a coleus or geranium, 

 which has been some hours in sunlight. Place it in hot 

 alcohol until the green color disappears, and then add some 

 iodine. The parts which were green are colored violet- 

 brown, indicating starch, but the white parts are un- 

 colored. Another leaf covered with dark cloth for 

 twenty -four hours will show little or no starch any- 

 *i where, indicating the removal in darkness of the 



starch formed in sunlight. 



204o. The opening bud of a 

 beech is a good example for ob- 

 servation of growth, as it ex- 

 pands from day to day. The long scales of 

 the winter bud become looser, and gradually, 

 by the elongation of parts between them, 

 the scales are forced apart, showing at the 

 base of each a minute leaf of perfect form. 

 Daily the leaf increases in size, the internodes 

 or stem portions between the leaves elongate, 

 the scales fall away, and from a bud of an 

 inch in length, by elongation throughout its 

 whole extent we have a leafy twig of many 

 inches, with a terminal bud, and a bud in the 

 axil of each leaf. The beginning of the spring 

 growth is likewise well shown in the pear 

 bud, Fig. 42. Consult Bailey's "Lessons with 

 Plants," pp. 44-72, for fuller discussions, with 

 many illustrations, of the opening of buds. 



205a. Mark a young stem, as at A in Fig. 

 43 ; but the next day we shall find that these marks are farther 

 apart than when we made them (B, Fig. 43). The marks have 

 all raised themselves above the ground as the plant has grown. 



Fig. 4j. The root 

 grows in end portion. 



