Vernalization 



and photoperiodism 



Plate 7 

 to face p. 87 





e^3^ til '-■ 







Ss 





■h e. 





Fig. 6. — Section through the apical meristem of a 

 veijetative soybean plant (14-hour photoperioci). X 120. 

 Note rounded tip. 



Fig. 7.~ -Section through the apical meristem of a 

 reproductive soybean plant (7-hour photoperiod), X 120. 

 Note flattened tip, the first microscopically visible sign 

 of induction of reproduction, and prominent axillary 

 meristem.— Photographs by the author. — Cf. p. 57. 



Fig. 8. — Rudbcckia hicolor i)lants. 86 days old. On 

 risht. vegetative plant -ro^iette with extremely inhibited 

 stem photoperiodic inhibition (short days). On left. 

 reproductive plant, with full development of stem (long 

 days).— Cf. p. 49. 



Fio. 9. High temperature induced flowering in Rud- 

 hcckia hicolor plants grown in a relatively hot green- 

 house. On right, reproductive plant (long days and 

 high temperature). On left, reproductive plant (short 

 days and high temperature). Note inhibited stem 

 elongation photoperiodic inhibition, but induction of 

 reproduction, by relatively hii*h temperature. 



