.364 Epinasty and Hyponasty of Raphanus Cotyledons. 



tropic." Early last spring Professor MacMillan of the University- 

 brought a plant of Solanum tuberosum from the greenhouse and 

 placed it upon a desk in his lecture room. The plant while in the 

 greenhouse was under the influence of strong illumination. In 

 the lecture room it had only diflfuse light. In the course of 24 

 hours a remarkable change took place in the position of the leaves. 

 Instead of being horizontal or slightly epinastic as they were un- 

 der normal conditions, they were curled downwards so that the 

 tips touched the stem. At the same time transverse epinastic 

 curvatures had taken place.ff 



This seemed to show that the absence of light of a certain 

 degree of intensity tends to promote epinastic curvatures. It 

 was a realization of this peculiar state of our knowledge regard- 

 ing epinasty and hyponasty that led Professor MacMillan to sug- 

 gest to me the advisability of selecting some normally epinastic 

 dorsi ventral organ and subjecting it to varying degrees of inten- 

 sity of light, as well as to varying intensities of light from differ- 

 ent directions. Not only was a study of the action of light upon 

 such an organ suggested, but also of all other natural conditions 

 which might influence epinastic or hyponastic growth. 



For this purpose the cotyledons of Raphanus sativa have 

 been chosen. So far as I have been able to determine, no con- 

 tinuous observations have been made upon the epinastic and 

 hyponastic curvatures of these normally epinastic organs. 



The experiments were conducted in the University green- 

 house, and the temperature in all cases was approximately the 

 same, varying from a minimum of 6o°-65° Fahr. by night, to a 

 maximum of 75°-8o° by day. 



The seeds were planted Dec. 20th, in four-inch flower-pot 

 saucers, and were constantly kept at the same degree of moisture. 

 Before proceeding to a consideration of the phenomena observed 

 it might be well to note in regard to the germinating seed of 

 Raphanus, that in all cases when the cotyledons break from the 

 seed-coats they are folded together, the lower and larger cotyle- 

 don always being strongly hyponastic, while the smaller and inner 

 cotyledon is always strongly epinastic. 



Two groups of cultures were made : 



A. Those grown under normal conditions from the first. 



B. Those grown under special conditions from the first. 



ft MacMillan: Botanical Gazette, Vol. xv, p. 121. 



