Stimulation and Correlation. 



131 



fruit pendent, and various combinations of growth and move- 

 ment of the separate parts may be made in order to accom- 

 plish the purposes of pollination and seed dissemination. 

 The character of these movements may be best understood by 

 discussion of the following types : 



142. Carpotropic movements of pedicels of Clay- 

 tonia Virginica. — The unopened flower buds are held in a 

 drooping position by a 



general curvature of the 

 short pedicel. The ad- 

 vanced stage of develop- 

 ment of the bud is the 

 signal for the straightening 

 of this curve until the open 

 flower is held erect, while 

 the mature flower is sub- 

 ject to the daily opening 

 and closing, as described 

 above. As soon as ferti- 

 lization ensues, the signal 

 thus set up starts two activ- 

 ities in the pedicel. The 

 pedicel begins a rapid 

 elongation which doubles 



• .1,1 J , Fig. 105. — I, 2, 3, 4, successive positions 



Its length, and a curvature „f ^^^^^ ^^ „^|,„„,^ f-.v^/^,-... (spring 



ensues in the extreme ba- beauty). 



sal portion by which the 



ripening pod is held in a pendent position most suitable for 



the dissemination of the seeds. (See Figs. 104 and 105.) 



Examine the position of the flower buds, open flower, and 

 seedpods of any plants accessible, and sketch positions. 

 Note stages in which movement occurs. 



143. Carpotropic curvatures of Streptocarpus 



Streptocarpus Rexii bears a number of striking flowers, each 



