Bums, Regeueratioii and its relation to trauniatioijiöin. 



163 



No. of Time in hori- Time in vor- Time in reversed Time on klino- Ilesults when re- 



seeds. zontal position tical ijosition liorizontal position. stat in casts. 



Ihr. 

 llir. 



2hrs. 



10 10 min. 



6hr: 

 Ihr. 



moved froni casts 



and rovolved on 



klinostat. 



Kesponded to 

 first Stimulus. 



ditto. 



Responded to tlie 

 second Stimulus. 



Grew straight. 



ditto. 

 9 grew straight 

 1 developed the 



curve. 



A study of this table shows that roots are able to hold the 

 influence of a geotropic stimidus for a very short time only. It 

 would be interesting to determine the exact length of tinie but 

 from the standpoint of this paper it is not essential. 



Auatomical studies. 



In the foregoing experiments it has been noted that the roots 

 tiu'iied down in answer to gravity after a eertain length of time. 

 Roots were killed and sectioned longitudinally to study their 

 structui'e at the time when this change took place. Those 

 roots were selected on which the brov»-n mass of dead tissue still 

 remained. This usually dropped off during the process of im- 

 bedding but by using a large part of the root it was not hard 

 to get sections through that jDai't of the root which had been 

 wounded. A study of these sections shoAved no trace of the 

 wound. The process of regeneration was completed. 



A series of sections was now made from roots which had 

 been wounded and which still showed a 

 marked traumatropic cui*ve. Figure 4 shows 

 part of the longitudinal section of a root 

 which was kiUed 48 hours after wounding. 

 At the time it was killed it was o-rowin«: 

 at an angle of 90 degrees. The ligm-e shows 

 that the wound has not been regenerated 

 l)ut that process is still going on. 



Fiff. 4:. 



Disciissioii and couclusioiis. 



A review of the facts obtained by the experimental work 

 cited in the preceding pagos show that the two phenomena. re- 

 generation and traumatropism, are very closely connected in the 

 case of the root-tips examined. 



The tirst set of experiments, taken in connection with the 

 anatomical work, show clearly that as long as wounded tissue is 

 found, the root will form a traumatropic curve. Or in other 

 words. when the process of regeneration is complete the Stimulus 

 causing the curv(; is removed. This seems to show then, that 

 there is a constant irritant and that the latent period is not 



11* 



