156 GROWTH AND WORK OF PLANTS 



outside of the exposed stigma. The two parts of the stigma 

 now open outward and become recurved, thus exposing the stig- 

 matic surface which is on the inner face. The pollen being 

 caught on the hairs of the outer surface of the lobes of the style 

 cannot come in contact with the inner stigmatic face. Now that 

 the parts of the stigma become recurved and the stigmatic sur- 

 faces exposed, the pollen from certain flowers is brushed onto 

 the stigmatic surfaces of others by insects which crawl in great 

 numbers over the disk flowers, and thus cross-pollination is 

 brought about. The style in the course of 12 to 24 hours then 

 contracts and is drawn down again into the corolla tube. This 

 took place in the cases which I have observed during the late 

 afternoon and evening. In the cases observed by myself the 

 anthers are drawn into the corolla tube at an earlier time during 

 the previous evening and night. Some movement takes place 

 during the day also, and some flowers lag behind, so that the 

 process is going on continually, but the greater amount of change 

 appears to go on during late afternoon, during the night, and 

 in the early morning. 



259. Ray flowers. The ray flowers have a rudimentary 

 ovary with which the calyx is consolidated, but the pistil is other- 

 wise undeveloped and stamens are wanting. Such flowers are 

 sterile, and are often called neuters. The corolla, however, is 

 very conspicuous. The petals are united by their edges in such 

 a way as to form a long, broad, leaf-like organ, except at the 

 base where they form a short tube. The ray flowers of the 

 sunflower do not show w r ell the number of divisions of the corolla. 

 But the ray flowers of some other composites do, as in the core- 

 opsis, etc., where the end is five-toothed. In many composites 

 the ray flowers are pistillate, and therefore develop seed like the 

 disk flowers, as in the ox-eye daisy, or white weed. In the dan- 

 delion, chicory, etc., all of the flowers are strap-shaped (like the 

 ray flowers) and are fertile. For composites of economic impor- 

 tance see Chapter XXXVI. 



260. The composite flower shows the highest degree of spe- 

 cialization, by the union of parts and the massing of the flowers, 



