196 STTTDr OP COMMON PLANTS. 



If enough species have been examined the characters 

 thus derived will be those of the Rosaceae or Rose Family, 

 a large and important natural order, furnishing a large 

 proportion of the fruits of the north temperate zone, 

 numerous ornamental species, among them the rose, 

 spiraea, hawthorn, and mountain-ash, and some medicinal 

 plants, including the wild cherry and others. 



The flowers of the various genera exhibit interesting 

 peculiarities of color and structure corresponding to the 

 different degrees of adaptation to insect visitors.^ 



SPECIAL STUDIES. 



I. Development of a cherry. This involves a study 



of the ovary and its changes during the entire 

 period of the formation of the fruit. Sections of 

 different specimens should be made at frequent 

 intervals, and a series of drawings kept with their 

 accompanying dates. 



II. A similar study of the development of the apple. 



III. How far the production of our domestic fruits is 



dependent on the agency of insects. 



IV. Evidence regarding the "law of progressive colora- 



tion " drawn from the flowers of this family.^ 



V. Collection and classification of the indigenous rosa- 

 ceous plants of the region in which the study is 

 carried on. 



VI. Origin and varieties of the cultivated strawberry. 



VII. Extra-floral nectaries and their use. 



1 Cf. Miiller, Fertilization of Flowers, pp. 242, 243. 



2 Allen, Colors of Flowers, p. 25 et seq. 



