CHAPTER XV 



THE INHIBITORY EFFECT OF AN APICAL LEAF ON 

 SHOOT FORMATION IN A STEM SUSPENDED 



HORIZONTALLY 



The account of the inhibitory effects of an apical leaf on the 

 shoot formation in young stems given in Chapters XII and XIV is 

 incomplete since it was concerned only with phenomena of inhi- 

 bition in a stem suspended vertically and upright. When a 

 stem is suspended horizontally and there is only one leaf at the 



Fig. 100. — Stems originally horizontal but with leaf on upper side. No shoot 

 or shoots formed on lower side in second node basally from leaf. Mar. 16 to 

 Apr. 3, 1923. 



apex of the stem the phenomena of inhibition vary according as to 

 whether the leaf is on the upper or the lower side of the stem. 

 This is illustrated by the Figs, 100 and 101. The four stems used 

 in these experiments were originally perfectly straight and were 

 suspended in moist air. The two stems in Fig. 100 had the apical 

 leaf on the upper side of the stem and the two stems in Fig. 101 

 had the apical leaf on the under side. The anlagen for the apical 



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