CYTOST IN THE PLANT WORLD 253 



As a result of these experiments Spaulding con- 

 cluded that traumotropism follows the application 

 of any agent which irritates strongly without killing 

 the plant. This conclusion coincides nicely with the 

 deductions made by the author as a result of his ex- 

 periments with animals. 



Numerous investigations by various botanists have 

 shown conclusively that the actual growth process 

 which accompanies the phototropic, thigmotropic, 

 and traumotropic responses of plants take place, not 

 at the site of injury, but at some distance from it, due 

 presumably to the diffusion of cytost through the 

 plant. In this respect, then, we find a rather crude 

 analogy to the behavior of cytost in the animal body, 

 where, it will be remembered, the distinctive action 

 of cytost becomes manifest in the splanchnic area at a 

 considerable distance from the original site of in- 

 jury. 



Loeb (1924) in his exhaustive experiments on re- 

 generation in Bryophyllum calycinum has shown that 

 a quantitative relationship exists between the amount 

 of regenerated shoots and roots and the mass of leaves 

 and stems exposed to illumination. This was to be ex- 

 pected, for the mass of material employed in the 

 regenerative process must arise from the photosyn- 

 thetic activities of the leaves. Loeb accounted for the 

 fact that mutilation leads to growth in portions of the 

 organism where no growth would have occurred 

 otherwise by assuming that, following mutilation, an 

 increased concentration of sap took place at the site 

 of the injury. These conclusions of Loeb's are satis- 

 factory in so far as they account for the accretion of 

 the material necessary for the new growth, but they 



