Composite Flowers. 



95 



lar to a in Fig. 77 ? Remove one of these ray flowers and 

 compare with the figure. Find the inferior ovary and the 

 pair of stigmas. Note that the ray is really a corolla with 

 petals united into a flat apparently simple petal instead of 

 into a cup or tube. Look for central or disk flowers similar 

 to/" in the figure. Look for the peculiar calyx limb called 

 pappus. It "may consist of scales or of hairs, and these 

 vary greatly in appear- 

 ance. Sometimes the pap- 

 pus is obsolete. Find in 

 the disk flower the stigmas 

 and the tube of anthers 

 which encloses them. 

 Note the appearance of 

 the involucre formed by 

 bracts outside the rays. Is 

 there a bract subtending 

 each disk flower? These 

 bracts called chaff may 

 be wanting, and usually 

 they are inconspicuous. 



Are any of your spe- 

 cimens made up entirely 

 of disk flowers? Of ray 

 these differences. 



Since these dense heads of flowers resemble single flow- 

 ers they are called compound or composite flowers, and the 

 separate flowers are called florets. Draw some of the larger 



a 



Fig. 77. Representing florets of tar-weed [See 

 page 4] and sunflower, a. A ray floret of tar-weed 

 and the enclosing bract which is covered with 

 tarry hairs, b. The bract enclosing the ripe akene. 



c . Ray floret magnified, with all but the base of the 

 corolla removed so as to show the pair of stigmas. 



d. Ray corolla, e. A disk floret magnified. The 

 disk florets are all sterile, producing only pollen. 

 /. Disk floret of sunflower, g. A ray floret of the 

 same. In sun-flowers the ray florets are sterile and 

 the disk florets are fertile. 



flowers? Classify according to 



