on the Mimosa ptidka. 61 



To prove, then, that impressions made at one part of the plant 

 are conveyed to other parts, following M. Dutrochet, I concen- 

 trated the rays of light by means of a lens on one of the extreme 

 leafets, and found that immediately afterwards this leaflet, with 

 its fellow on the opposite side, closed ; and that the impression was 

 conveyed down the petiole was evident, from the leaflets below 

 closing in succession downwards ; then the leaflets of the second- 

 ary petioles on each side closed from below upwards, or towards 

 the extremity of the leaf; shewing whence the impression came, 

 and its course. Much about the same time, the secondary peti- 

 oles supporting the leaflets approached each other in a lateral 

 direction ; then the primary petiole bent itself down towards the 

 ground. Sometimes this was all that happened, and occasionally 

 the impression did not go so far ; but generally when the sun- 

 shine was bright, it was conveyed to the other leaves of the plant, 

 for the most part to those above and below first, then to the 

 next in vicinity ; sometimes, however, the impression was mani- 

 fested first in those leaves at a considerable distance from that 

 on which the stimulus was applied ; the first effect on which was 

 the bending of the petiole towards the ground, the next the ap- 

 proaching of the secondary petioles, and, lastly, or about the 

 same time, the closing of the leaflets in pairs, in each of the 

 secondary petioles, from the base towards the extremity of the 

 leaf; the motion being reversed in regard to that in the leaf 

 stimulated. Such, then, were the general effects of the concentra- 

 tion of the sun's rays and other stimuli on the leaves of the 

 sensitive plant. The Mimosa pudica, however, frequently closes 

 all its leaves in the bright sunshine, the primary petiole being 

 then, as far as I have observed, generally in an erect position, 

 the leaflets and secondary petioles only being flexed ; the same 

 happens at night, with considerable flexion of the primary 

 petiole ; also in cold weather, and on the application of many 

 stimuli. I remember several years ago, being very much asto- 

 nished at the effect produced by cold water on the Mimosa pudica. 

 During bright sunshine, I poured a quantity of cold water into 

 a plat in which the flower-pot, containing the plant, was standing; 

 immediately after which, the leaves rapidly flexed themselves to- 

 wards the ground ; the secondary petioles and then the leaflets 

 closed.. That it was by the roots that the impression was con- 



