MOVEMENT IN RESPONSE TO INJURIES 



35 



lieved are connected with the transmission of the effects of the 

 stimulus. Such effects may be observed by wounding roots by 

 incisions with a razor, and then fixing a half hour or hour later in 

 a mixture of picric, acetic and sulphuric acid in water. The ob- 

 jects are stained in toto and sectioned by the usual imbedding 



f\ 



FIG. 1 8. Diagrammatic representation of the regions in which transmission of the 

 primary (/) and secondary (//) effects of wound-stimuli take place in the roots of 

 Allium cepa. Stimulus given at S and roots fixed 12 minutes later. 5 shows the re- 

 gion affected in the inner periblem. 6, the region affected in cross-section through the 

 point of incision. 7, the region affected as shown by a radial section through the 

 point of incision. After Nemec. 



methods. Transmission of the traumatic impulse takes place as 

 shown by these reactions most readily in the median and inner 

 periblem. 



51. Movements of Mimosa in Response to Injury. Secure a 

 few well-grown specimens of Mimosa and place them in a room 

 at 25 to 30 C. Snip off the terminal pair of pinnules with 

 a sharp pair of scissors and note the reaction. Touch the tips of 

 another leaflet with a lighted match or a heated rod. Cut a slit 

 in the lower part of the stem of a specimen with expanded leaves 

 taking care not to jar the plant. Compare the rate of transmis- 

 sion with that shown in response to shock. Make a series of 

 wounds to determine whether injury stimuli are cumulative in 

 their effects. Note the exudation of water from the wounds. 



No definite purpose can be surmised for the reaction of Mimosa 



