52 THE VITAL FUNCTIONS. 



Cliondrilla ynuralis were carefully cleaned, and 

 immersed in filtered rain water : the water was 

 changed every two days, and the plant continued 

 to flourish, and put forth its blossoms : at the 

 end of eight days, the water had acquired a 

 yellow tinge, and indicated, both by the smell 

 and taste, the presence of a bitter narcotic sub- 

 stance, analogous to that of opium ; a result 

 which was farther confirmed by the application 

 of chemical tests, and by the reddish brown re- 

 siduum obtained from the water by evaporation. 

 M. Macaire ascertained that neither the roots 

 nor the stems of the same plants, when com- 

 pletely detached, and immersed in water, could 

 produce this effect, which he therefore concludes 

 is the result of an exudation from the roots, con- 

 tinually going on while the plant is in a state of 

 healthy vegetation. By comparative experiments 

 on the quantity of matter thus excreted by the 

 roots of the French bean (Phaseolus vulg-aris) 

 during the night and the day, he found it to be 

 much more considerable at night ; an effect 

 which it is natural to ascribe to the interruption 

 in the action of the leaves when they are deprived 

 of light, and when the corresponding absorption 

 by the roots is also suspended. This was con- 

 firmed by the result of some experiments he 

 made on the same plants by placing them, during 

 day time, in the dark, under which circumstances 

 the excretion from the roots was found to be 



