FLOWERS 



49 



Inside the bracts are the whorls of brightly colored, irregular flowers called 

 the ray flowers. They appear to act, in some instances at least, as an attrac- 

 tion to insects by showing a definite color 

 (see the common dogwood, Cornus florida). 



A composite head. 



Section through composite head, show- 

 ing a disk flower (a), a ray flower (c), 

 and the involucre (rf). 



In most cases the ray flowers are imperfect. 



Decide this in the aster or cosmos. (The 

 latter is easil3' obtained in the fall of the year.) Determine what parts of 

 the ray flower are missing. The flowers occupying the center of the cluster 

 are the disk flowers. Examine such a flower under the hand lens. Deter- 

 mine if the flower is perfect. A careful observer will find in cosmos that the 

 anthers are united in a ring around the pistil. This is a typical condition in 

 the Compositse. 



Reference Books'. 



for the pupil 



Andrews, Botany all the Year Round, pages 222-236. American Book Company. 

 Bailey, Lessons uith Plants, Part III, pages 131-250. The Macmillan Company. 

 Coulter, Plant Studies. Chapter VII. D. Appleton and Company. 

 Dana, Plants and Their Children, pages 187-255. American Book Company. 

 Hunter and Valentine, Laboratory Manual of Biology. H. Holt and Company, 

 Lea\att, Outlines of Botany, pages 118-127. American Book Company. 

 Lubbock, Flowers, Fruits, and Leaves, Part I. The Macmillan Company. 

 Stevens, Introdvx:tion to Botany, pages 171-206. D. C. Heath and Company. 



FOR THE TEACHER 



Darwin, Forms of Flowers. D. Appleton and Company. 



Darwin, Orchids Fertilized by Insects. D. Appleton and Company. 



Darwin, Fertilization in the Vegetable Kingdom. Chapters I. and II. D. Appletxjn 



and Company. 

 Campbell, Lectures on the Evolution of Plants. The Macmillan Company. 

 Gray, Structural Botany. American Book Company. 

 Lubbock, British Wild Flowers. The Macmillan Company, 

 ifear Book, U.S. Department of Agriculture, 1896, 1897, 1898, 1899, 1900. 



hunter's BIOL. — 4 



