FLOWERS, THEIR STRUCTURE AND KINDS 169 



271. The pistil. The ovary is narrowly wedge-shaped, four- 

 sided by compression. The style is long and slender, and the 

 stigma is divided longitudinally into two portions. The inner 

 plane surfaces fit closely together, and the outer hairy surfaces 

 are in contact with the anther locules up to and during the 

 early stage of flowering. 



272. Pecularities in the flowering of the disk flowers. 

 The mode of inflorescence is centripetal as described above, i.e., 

 it proceeds from the outside inward. At the time of flowering 

 the anther tube and the stigma which it surrounds are pushed out 

 of the corolla tube by the gradual elongation of the filaments 

 and the style, though the anthers are often slightly in advance of 

 the stigma (see figs. 123, 124 for details). This takes place, as I 

 have observed it, during the night and early morning. In the 

 course of two to four hours, the style having reached its full 

 length, the filaments shorten and draw the anthers down into 

 the corolla tube again. While this is going on the style remains 

 elongated, and the upright hairs on the outer face of the cleft 

 portion of the style catch the pollen as the open anthers are 

 dragged downward. The great mass of pollen is thus left on the 

 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 



