192 STUDY OF COMMON PLANTS. 



With the fruits of the sugar maple, compare those of 

 the red and silver maples, noting all the external and 

 structural differences by which they may be distinguished. 



Leaves. 



Compare -the leaves of all three kinds until you are able 

 to distinguish the species at sight by means of the leaves 

 alone. 



Finally review the observations made thus far, see if 

 anything is to be added, and write a complete account 

 of the characters common to all three species and also of 



those peculiar to each. 



* 



SPECIAL STUDIES. 



I. Critical comparison of the Box-elder, Negundo 

 aceroides, Mcench., with the maples. Does it have 

 the essential characters of a maple ? 



II. Polygamous plants. Cf. Darwin, Different Forms of 

 Flowers on Plants of the Same Species, Chap. VII. 



