Ohap. II. TO CONTACT. 127 



remained in this position for 15 m., but when looked at again 

 AO-m. after the rubbing, each had fallen 14°. Both cotyledons of 

 another and younger seedling were lightly rubbed in the same 

 manner for 1 m., and after an interval of 32 m. each had risen 

 30°. They were hardly at all sensitive to a fine jet of water. 

 The cotyledons of S. tfandii, an African water plant, are thick 

 and fleshy ; they are not sensitive and do not go to sleep. 



Mimosa pudica and albida. — The blades of several cotyledons 

 of both these plants were rubbed or slightly scratched with a 

 nt-edle during 1 m. or 2 m. ; but they did not move in the least. 

 "When, however, the pulvini of six cotyledons of M. pudica were 

 thus scratched, two of them were slightly raised. In these two 

 eases perhaps the pulvinus was accidentally pricked, for on 

 pricking the pulvinus of another cotyledon it rose a little. It 

 thus appears that the cotyledons of Mimosa are less sensitive 

 than those of the previously mentioned plants.* 



Vxalis sensitive. — The blades and pulvini of two cotyledons, 

 standing horizontally, were rubbed or rather tickled for 30 s. 

 with a fine split bristle, and in 10 m. each had risen 48° ; 

 when looked at again in 35 m. after being rubbed they had 

 risen 4° more ; after 30 additional minutes they were again hori- 

 zontal. On hitting a pot rapidly with a stick for 1 m., the coty- 

 ledons of two seedlings were considerably raised in the course 

 of 11 m. A pot was carried a little distance on a tray and thus 

 jolted ; and the cotyledons of four seedlings were all raised in 

 10 m. ; after 17 m. one had risen 56°, a second 45°, a third almost 

 90°, and a fourth 90° After an additional interval of 40 m. three 

 of them had re-expanded to a considerable extent. These obser- 

 vations were made before we were aware at what an extraordi- 

 narily rapid rate the cotyledons circumnutate, and are therefore 

 liable to error. Nevertheless it is extremely improbable that the 

 cotyledons in the eight cases given, should all have been rising 

 at the time when they were irritated. The cotyledons of Oxalis 

 Valdiviana and rosea were rubbed and did not exhibit any 

 sensitiveness. 



Finally, there seems to exist some relation between 



* The sole notice which wo p. 865), " les cotyledons du M 



Iiflvo met with on tlie sensitive- pwdica tendent a se raproclicr pal 



ue.s of cotyledons, relates to Mi- leurs faces superieiircs loraqu'on 



mosa ; for Auir. P. De Candnlle les irrite." 

 wys ('Pliys. V^g.,' 1832, torn. ii. 



