132 



Elementary Plant Physiology. 



on its separate peduncle, which is curved in such manner 

 that the unopened bud is held in a drooping position, or 

 variously inclined, as in Fig. 106. As the development of 

 the flower proceeds, and the stamens and pistils mature, the 

 opened corollas are held in a horizontal position until fertiliz- 

 ation is accomplished, when the apical portion of the peduncle 

 again takes up a motion by which its curvature is straightened 



until the capsule is held 

 in an approximately erect 

 position. The signal or 

 stimulus for each of these 

 motions is set up by the 

 plant itself. Thus the 

 growth and enlargement 

 of the flower bud stimu- 

 lates the peduncle in such 

 manner that it performs a 

 straightening of the curva- 

 ture until the corolla tube 

 is held in a horizontal 

 position. At this point 

 the movement ceases, and 

 the flower is held firmly 



Fig. 106. Positions of buds, flowers, and pods j n this position until pol- 

 of Streptocarpus Rexii. 



len has been deposited on 



the pistil, and presumably the growing tubes from the ger- 

 mination of the pollen have reached the egg cell. The fusion 

 of the nucleus from the pollen tube and that of the embryo 

 sac sets up another signal or alarm, which again sets the 

 peduncle in motion, and the pod is slowly erected into the 

 position shown in the figure. 



144. Complex movements of inflorescence of Al- 

 lium. The inflorescence of Allium Neapolitanum is enclosed 

 in sheathing bracts and supported in a drooping position on 



