710 



PHYSIOLOGICAL BASIS OF POLARITY. II 



Fig. 21. Stems with leaf at base suspended in moist air. Roots developed first 

 in some of the more apical nodes of the stem and persisted even after the basal 

 roots had formed. The latter, being air roots, grew too slowly to inhibit the 

 growth of the more apical roots. Drawn after 30 days. 



