76 Introduction to Botany. 



from the base to the summit of the stem ? Draw types of 

 the different kinds. 



78. How does the angle made by the leaf with the stem 

 vary as the leaf advances from its embryonic condition in 

 the bud to maturity ? Does the direction taken by the 

 stem seem to affect this angle ? To answer this question 

 study the approximately horizontal and vertical branches 

 of the same plant. 



79. What is the position taken by the leaves with refer- 

 ence to the incident light ? 



Note the position of leaves at different times of the day 

 to find out whether the movement of the area of greatest 

 light from the east toward the west affects the positions of 

 leaves, and if so, to what degree. 



80. Determine the angular divergence of the leaves. 

 (See page 48.) 



8 1. Is there any relation between the breadth of the 

 leaves and the number of vertical rows on the stem ? 

 When the vertical rows are numerous, are the leaves more 

 narrow as a rule than when the rows are fewer ? 



82. Is there any definite relation between the lengths of 

 the leaves and their vertical distances apart? It should 

 be remembered that short leaves will permit the light to 

 strike between them better than long ones. 



83. When leaves are growing close together in the form 

 of rosettes, how are they prevented from shading each other 

 too much ? Notice whether there is a difference between 

 the lower and upper leaves as to their size and shape, and 

 their angular deviation from the horizontal. 



84. In trees and shrubs, do the leaves on the horizontal 

 branches grow from buds on the lower as well as on the 

 upper side ? Do the leaves seem to assume a definite 

 position with reference to the light from above ? 



