A MANUAL OF BOTANY 39 



Study of forms. Observe the general form of the leaf. 

 What peculiarities of thickness, leaf margin, and surface do 

 you observe ? Determine the fitness of the leaf in all par- 

 ticulars to remain long on the plant and its adaptation to 

 great moisture and heat, or to great cold. Examine a 

 "transverse section of a leaf (Ip.), and compare with that 

 of the geranium, Make drawings showing the various 

 leaves and the details of structure. 



How can you explain the presence of such broad, ever- 

 green leaves on the vinca, exposed, as it may be, to great 

 cold, whereas most leaves of this character (broad) are 

 found on trees of warm and moist regions ? Are the leaves 

 really evergreen ? Compare them with the narrow-leaved 

 evergreens, like the pine of cold countries, and observe the 

 great difference in size and form, and seek carefully for an 

 explanation of the difference. 



IMake a list of ten forms of each kind, stating where each 

 is found. 



7. Leaf Experiments and Determination of Leaf 

 Functions ^ 



1. Grow some oats in the dark in a deep narrow glass jar, 

 and at the end of 5 or 6 days observe the color of the 

 leaves. What is the explanation ? 



2. Place a small vigorous geranium in total darkness, for 

 the same length of time, keeping it well supplied with 

 water. From the two experiments what is necessary for 

 the healthy chlorophyll formation ? 



3. Place a vigorous leafy shoot in a small bottle of water 

 and seal about the stem with wax. Place under bell jar. 

 What is the result? The process or function illustrated 

 here is called transpiration. 



1 Other exi)crinieiits, other than the ones ^iven, may suggest them- 

 selves. 



