Chap. II. CLEMATIS. 55 



with which it is left in contact. The inferior surface 

 of the rectangularly bent terminal portion (carrying 

 the terminal leaflet), which forms the inner side of the 

 end of the hook, is the most sensitiye part ; and this 

 portion is manifestly best adapted to catch a distant 

 support. To ^ show the difference in sensibility, I 

 gently placed loops of string of the same weight (in 

 one instance weighing only '82 of a grain or 53"14 mg.) 

 on the several lateral sub-petioles and on the terminal 

 one; in a few hours the latter was bent, but after 

 24hrs. no effect was produced on the other sub-petioles. 

 Again, a terminal sub-petiole placed in contact with a 

 thin stick became sensibly curved in 45 m., and in 

 Ihr. 10m. moved through ninety degrees; whilst 

 a lateral sub-petiole did not become sensibly curved 

 until 3 hrs. 30 m. had elapsed. In all cases, if the 

 sticks are taken away, the petioles continue to move 

 during many hours afterwards; so they do after a 

 slight rubbing ; but they become straight again, after 

 about a day's interval, that is if the flexure has not 

 been very great or long continued. 



The graduated difference in the extension of the 

 sensitiveness in the petioles of the above-described 

 species deserves notice. In G. montana it is confined 

 to the main petiole, and has not spread to the sub- 

 petioles of the three leaflets ; so it is with young plants 

 of 0. calycina, but in older plants it spreads to the 

 three sub-petioles. In G. vitieella the sensitiveness has 

 spread to the petioles of the seven leaflets, and to the 

 subdivisions of the basi-lateral sub-petioles. But in 



