THE STRUCTURE AND FUNCTION OF HIGHER PLANTS 85 



cocklebur plant is caused to flower in the middle of the summer bv ex- 

 posmg It to short day conditions, other plants may be caused to flower 

 by grafting them to the plant which was originally treated with short day. 

 If one branch of a cocklebur plant is induced to flower by exposing it to 

 short day, all of the branches on the plant will flower whether or not they 

 are exposed to long day or complete darkness. iMany types of plants re- 

 spond in a manner similar to cockleburs. Grafting experiments have shown 

 that the stimulus for flowering may be transmitted from one species of 

 plants to another. 



All of this evidence indicates the presence of a hormone for flowering. 

 Of course, one must realize evidence for a flowering hormone is circum- 

 stantial. We will not be able to say with certainty that such a hormone 

 exists until the chemist has identified it, synthesized, and produced its 

 effects by injecting it. 



Assuming that scientists can find out what this hormone is, the point 

 may be raised of whether or not this discovery will prove important. There 

 is little difficulty in stating its value. It would be hard to speculate as to 

 what we might expect this new hormone to do, but an attempt to draw a 

 parallel with the discovery of auxin could be made. One may wonder 

 what importance would have been attached to the efforts of the early 

 plant scientists who were trying to discover the plant hormone which 

 caused little oat seedlings to bend toward the light. It is quite possible 

 that no one foresaw the applications which would be made of this hor- 

 mone after its discovery. The plant scientists working on this problem 

 spent much of their time in dark basements where they grew their 

 seedlings, and they were considered useless but probably harmless, by 

 their neighbors, even by their fellow scientists. Yet we know of the great 

 developments which have come from their discoveries. Thus we can 

 reasonably assume important practical applications of the flowering hor- 

 mone after its isolation and synthesis. 



^y ^^ ^'^ 



