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Regeneration and its relation to traumatropism. 



Bv 

 George P. Bums. 



(Witli 4 iniages iu tlie text.) 



It is a well known fact tliat plants are able to regenerate 

 tissne at tlie root-tip, wlien such tissue lias been destroyed, altlioug-h 

 tlie injmy be so great tliat tlie entire tip be renioved.^) It is 

 equally well known tliat wlien root-tips are wounded in any manner 

 such as burning with a hot glass rod, cutting etc., witliin the 

 sensitive zone, that they respond to the Stimulus, developing a 

 traumatropic curve.^) The intensity of this curve varies within 

 large limits. In sonie cases the roots describes two circles while 

 in others the angle of divergence from the perpendicular is very 

 small. Those roots which develop the extreme curves were injiu'ed 

 very severely and die alniost without exception, the plant depending 

 upon the development of lateral roots. 



The preeeeding observations show that botli regeneration and 

 traumatropic curvature follow the same Stimulus. On this point 

 Spalding says,^) „the phenomena go hand in band, and it seems 

 impossible not to regard them as two different fornis of Nach- 

 wirkung resulting from the same cause'". 



The relation of regeneration to traumatropic curvatm-e as 

 Seen in the root-tip has not been, as far as I know, a subject of 

 special consideration. Spalding refers only to the biological 

 sign iflca nee of the traumatropic curve wlien considered in connec- 

 tion with regeneration. He says, „In case of injury to the growing 

 point of the root it is essential to the welfare of the plant that 

 repair should take place as promptly and economically as possible. 

 This is accompHshed with remarkable rapidity by the j)rocess of 

 n^generation. Mean while it is also important that while the work 

 of repaii- is going on the root shoidd avoid further contact with 



the source of injury This is brought about by traumatropic 



curvatiu'e " 



In this same j^aper one division is devoted to a study of 

 „Suspension of growtli and its Relation to Traumatropic Curva- 

 ture'". Roots of Lupiiius albus, Vicia Faba, and Zea Mais were 

 wounded and placed in plaster-casts. The casts were then placed 

 in meist saw-dust in such a position that the roots were perpen- 



