"Fig. 4. 



Fig. 5. 



Figs. 4 and 5, Six stems split longitudinally each half stem possessing one 

 apical leaf. Half stems in Fig. 5, kept in dark, produce practically no roots 

 while the half stems in Fig. 4, exposed to light, form an abundance of air roots. 

 Duration of experiment 22 days. 



693 



