BUD INHIBITION 215 



factors involved in bud growth. In etiolated Pisum seed- 

 lings the factor (or factors) necessary for growth in length 

 of the stem or branch could be separated from factors govern- 

 ing leaf development and embryonic bud growth by cutting 

 off different parts. The former comes mainly from the roots 

 and to a less extent from the cotyledons, the latter mainly 

 from the cotyledons. He suggested that the auxin coming 

 from the terminal bud may influence the upward movement 

 of the factor necessary for bud growth. Wherever an auxin 

 production center is located, it would cause the bud-growth 

 factor to move towards that place, preventing other, non- 

 auxin producing, buds from obtaining this factor. This 

 would be one way to explain the curious fact that the growth 

 of laterals is inhibited by auxin coming from the terminal 

 bud, but promoted by auxin produced in their own tissues. 

 However, Le Fanu's (1936) observation of the inhibition 

 due to basal application of auxin would also explain this. 

 In XI E evidence has been given that auxin causes a redis- 

 tribution of the specific root-forming factor, w^hich would be 

 comparable to the action suggested above. This \dew is 

 essentially a revival of the old hypothesis (see e.g. Goebel, 

 1903; Loeb, 1915) that the growing point is a ''center of 

 attraction" for the material necessary for stem growth. 



The factors controlling bud growth are apparently subject 

 to polar distribution in rhizomes, as Schwanitz (1935) has 

 shown. If the rhizome is cut up immediately on removal 

 from the plant, then each piece produces about the same 

 number of buds, but if it is first placed in the ground for 

 16 days or so, and then cut up, the majority of the buds 

 are formed in the apical portion. 



One of the factors for growth in length is apparently 

 biotin, since Kogl and Haagen Smit (1936) have described 

 how markedly it increases the growth in length of Pisum 

 seedlings from which the cotyledons have been removed. 

 Eastcott's finding (1928) that large quantities of bios are pres- 

 ent in germinated malt seems significant in this connection. 



The influence of factors other than auxin may explain 



