BUD INHIBITION 



211 



In this connection it is significant that many dwarfs, such 

 as those of Pisum, Vicia, and Zea, have a bushy habit, i.e. 

 the buds in their lower nodes develop extensively. If the 

 dwarfing is due to a reduction in the amount of auxin 

 present, as is true for the nana form of Zea Mays (van 



Fig. 59. Bud inhibition in etiolated Pisum seedlings. Nos. 1-5, decapitated 

 below terminal bud; 6-9, decapitated below upper lateral bud; 10, intact 

 controls. Auxin paste applied to apex immediately after decapitation. Con- 

 centrations: for 1 and 6, 10 mg.; for 2 and 7, 2.5 mg.; for 3 and 8, 0.6 mg.; for 

 4, 0.15 mg. indole-acetic acid per gram lanoline; for 5 and 9, plain lanoline. 



Overbeek, 1935), then the branching is doubtless due to the 

 same cause. 



The above experiments leave no doubt that in Vicia and 

 Pisum auxin is the factor inhibiting lateral bud growth. 

 The same is true in other plants. Muller (1935) apphed 

 lanoHne pastes containing urine, or orchid pollinia, to a 

 number of decapitated plants other than those already men- 

 tioned. In Sinapis, Linum, Antirrhinum, Godetia, Zinnia, 

 Helianthus, and Tradescantia, the pastes caused inhibition 

 of lateral bud development, but in Polygonum and Tropaeo- 



