66 



LIGHT AND THE BEHAVIOR OF ORGANISMS 



B 



<^o4^- '"^-^ 9:40 A.M. 

 11:00 

 .11:30 



12:30 P.M. 

 1:00 



1:55 



2:30 



d 



9:15 A.M:. 



10:00 



Fig. 6. A-E. Courses taken by tips of plumules in bending toward the glower 

 in a graded beam of light; magnified five times. The dots represent the position 

 at time indicated. The large arrows indicate direction of rays; the small ones the 

 direction of movement of plumules; d, side of the beam having the lowest light 

 intensity; /, side having highest intensity. In E the beam was reversed between 

 i.ooand 2.00 p.m. It will be seen that in every case except A the plumules de- 

 flected slightly toward the more highly illuminated side. See text. 



d. Results. — Under these conditions the reactions of 

 36 plumules, 14 of wheat (Triticum vulgare) and 22 of corn 

 (Zea mays), were studied and recorded with the following 

 results: of the 14 wheat plumules studied 6 deflected toward 

 the more highly illuminated side, 3 toward the less highly 

 illuminated side, and 5 did not appreciably deflect in either 

 direction. Of the 22 corn plumules 13 deflected toward th^ 

 more highly illuminated side, 2 toward the less highly 



