

FLOWERS, THEIR STRUCTURE AND KINDS 



167 



called ray flowers. The disk flowers are very great in number 

 and occupy the space inside of the circle of ray flowers. The 

 corolla is tubular in form, and the disk flowers are often called 

 tubular flowers. Each disk flower grows by the side of (really 

 in the axil of) a slender pointed bract. On the outside of the 

 head are a large number of overlapping green leaf -like members, 

 each with a long, narrow, pointed end. These are bracts which 

 together make up the involucre, which encloses the head in the 

 young stage. 



267. The disk flowers or tubular flowers. The flowers 

 should be studied in the different stages of flowering. The mode 



Fig. 123. 

 Tubular flowers of sunflower, showing details of flowering from left to right. 



of inflorescence is centripetal. The flowers on the outer margin 

 of the disk open first, while those in the center are still quite 

 young. These form a circle, and as they pass the height of the 

 flowering period another broad circle of flowers just inside the 

 outer ring come into the height of flowering. The circle of 

 flowers in the height of flowering is always very conspicuous, 

 because the stamens and the stigmas of the flower project so far 

 above the corolla tube at this time. Later the stamens and 

 stigmas shorten and become inconspicuous again (see figs. 123, 

 124). For the study of the flower several disk flowers in different 



