Dec, 1908.] 



The Effect of Alkaloids. 



411 



From this table it will be observed that strychnine, especially 

 in the stronger concentration acted poisonously upon the plants, 

 checking rather than stimulating their regenerative power. 

 Even a superficial examination of the Tables I and III will leave 

 no room for doubt as to the very large difference between the 

 first and the second regeneration in favor of the former. And in 

 spite of the fact that after the second operation the plants had 

 been regenerating for a longer period of time, the regenerated 



Fig. 5- 



Diagram of decapitated plants; <? — old epicotyl. 



d and r — regenerating stems. 



stems were bv far smaller than those regenerated after the first 

 operation. That the difference is not to be attributed to an 

 exhaustion of food materials was evident because the cotyledons 

 were still of a large size. Furthermore, McCallum (4) demon- 

 strated in a series of ingenius experiments that food is not a 

 necessary factor in regeneration of Phaseolus, and that the 

 plants regenerate even with the cotyledons removed. 



CONCLUSION. 



In summing up the facts presented in this note it may not be 

 amiss, perhaps, to discuss briefly their relation to facts obtained 

 in other similar studies. It was shown in the foregoing that 

 alkaloids, such as pilocarpine, atropine, strychnine and digitalin 

 exert a stimulating influence upon regenerating plants, increasing 

 the rate of regeneration. Yasuda (7) found from his study of 

 the effect of alkaloids upon moulds that "the moulds generally 

 grow better in the solutions which contain alkaloids than in the 

 normal control-solution." (p. 82.) He also found that strychnine 

 produced no poisonous action on the moulds until the limit of 

 saturation was reached (about 2.5%). Plants behave somewhat 

 differently in this respect from animals. In a recent work on the 

 effect of alkaloids upon the early development of eggs of the sea- 

 urchin, Toxopnenstes variegatus, conducted at the Bermuda 

 Biological Station (5c), atropine, strychnine and digitalin were 

 found to inhibit the developmental process, the last two sub- 

 stances being so much toxic that normal development was pos- 

 sible only in very dilute solutions. Neither did pilocarpine 

 stimulate or accelerate to any marked degree the development of 

 the eggs of this sea-urchin, although the literature contains a 



