Epinasty and Hyponasty of Raphanus Cotyledons. 367 



After 48 hours. Upper cotyledons epinastic, lower hyponastic. 



After 72 hours. Same as No. 4. A number of plants so placed as to 



throw direction of light rays toward notch between cotyledons. 

 After 96 hours. Cotyledons hyponastic. Those placed so as to throw 



illumination toward notch between cotyledons have closed. More 



may now be so placed. 

 After 120 hours. Cotyledons all strongly hyponastic. Separating, owing 



to the epinastic curvature of the hypocotyls. They have all turned so 



that the light is directed toward the notch. 



6. Exposed for 12 hours to total darkness, 6 to strong illu- 

 mination, 18 to total darkness, and 12 to diffuse daylight, (re- 

 peat.) 



These were planted Dec. 20th, 6 p. m. 



After 12 hours. Put in strong illumination. 



After 18 hours. Put in dark. Germinating. 



After 36 hours. Put in diffuse light. 



After 48 hours. Put in dark. Same phenomena of curvature as in A. 



After 60 hours. Put in strong illumination. Upper cotyledons epinastic^ 

 lower hyponastic. 



After 66 hours. Put in dark. Cotyledons strongly epinastic. In many 

 cases they are parallel. The epinasty of the upper cotyledon being^ 

 lessened, with tendency toward hyponastic curvature. The upper coty- 

 ledon does not become hyponastic, but does become less epinastic until 

 the lower cotyledon overcomes its hyponastic curvature. 



After 84 hours. Put in diffuse light. Cotyledons hyponastic, upright, sep- 

 arating, owing doubtless to the epinastic curvature of the hypocotyls. 



After 96 hours. Put in dark. Cotyledons hyponastic, but less so than 12 

 hours ago. 



After 108 hours. Put in strong illumination. Cotyledons hyponastic. 



After 114 hours. Put in dark. Cotyledons hyponastic, but less so than 6 

 hours ago. 



After 132 hours. Put in diffuse light. Cotyledons epinastic. 



After 144 hours. Put in dark. Cotyledons present a very peculiar appear- 

 ance. They are still slightly epinastic, but the edges are curled up- 

 wards, showing tendency toward hyponasty. 



After 156 hours. Put in strong illumination. Cotyledons epinastic with 

 edges curled upward. 



After 162 hours. Cotyledons epinastic, with edges not curled upwards. 

 The plants were now put in total darkness, and kept in 



this condition for ten days. Observations were made at 12 m. 



on each day, but in all cases they were strongly epinastic. Some 



of these were repeatedly exposed first to light then to darkness^ 



but this produced no further curvatures. 



7. Exposed for 12 hours to dark, 12 hours to diffuse light,, 

 18 to dark, 6 to strong light, 12 to dark, 6 to strong light, 6 to 

 diffuse light, 12 to dark, 6 to diffuse light, 18 to dark, and 12 

 to strong light. {Repeat). These also were planted Dec. 20th, 

 6 p. m. 



