UPON ELECTRICAL STIMULI GENERALLY 45 



** We are therefore left with the apparent discrepancy 

 already observed, . . . The work of the physiologists, 

 assuming it to be sound, certainly indicated that radium 

 emanation is capable of stimulating certain cell activities. 

 Sutton's results show that such stimulus, if it exists, does 

 not affect the final growth of the plant. This discrepancy 

 is periodically confronting the agricultural investigator." 



I know as little about radium as most people, but it is 

 eaid to discharge an electroscope and the alpha rays are 

 stated to be positively charged. An effect upon animal 

 cells has been that of over-ionisation which may certainly 

 be called stimulus but which when applied to normally 

 ionised tissue might well lead to a multiplication of centro- 

 fiomes and the exaggerated and irregular form of mitosis 

 associated with cancer. 



As regards the rest of the quotation I have made from 

 Dr. Russell's valuable work I need only say that for the 

 most part the experiments he describes as having been 

 attended by negative results are more indicative of groping 

 in the dark than of following and attempting to improve 

 upon natural laws. 



Writing upon the stimulus of light, Bose {Comparative 

 Electro-Physiology, p. 557) instances the very interesting 

 experiment of Sach's, in which a long shoot of Cucurbita 

 was made to grow inside a dark box, the rest of the plant 

 being exposed to light. 



** The covered part of the plant, under these circumstances, 

 showed normal growth of stem and leaves. Normal flowers 

 and a large fruit were also produced in the same confine- 

 ment. The tendrils inside the box, moreover, were found 

 to be fully as sensitive as those outside. The transmission 

 of stimulus by the plant, in such a way as effectively to 

 maintain such complex life activities as motility and growth, 

 even in the absence of direct stimulation, is thus fully demon- 

 strated. And we may gather an idea from this fact of the 

 fundamental importance, to the life of the plant, of those 

 nervous elements by which this is rendered possible. 



" One of the most important functions of the venation 

 of the leaf, not hitherto suspected, is now made clear to us. 



