32 MIL DAEWIN ON CLIMBING PLANTS. 



of C. calycina ; but in older plants it has spread to the three sub- 

 petioles. Iu C. viticella it has spread to the petioles of the seven 

 leaflets, and to the subdivisions of the basi-lateral sub-petioles. 

 In this latter species the sensitiveness has diminished in the basal 

 part of the main petiole, in which alone it resided in C. montana, 

 and has accumulated in the abruptly bent terminal portion. 



Clematis flammula. — The shoots, which are rather thick, straight, 

 and stiff, whilst growing vigorously in the spring, made small oval 

 revolutions, following the sun in their course. Four were made 

 at an average rate of 3 h. 45 m. The longer axis of the oval, de- 

 scribed by the extreme tip, was directed at right angles to the line 

 joining the opposite leaves ; its length was in one case only 14 } 

 and in another case If inch ; so that the young leaves arc moved a 

 very short distance. The shoots of tho same plant observed in 

 midsummer, when growing not so quickly, did not revolve at all. 

 I cut down another plant in tho early summer, so that by Au- 

 gust 1st it had formed new and moderately vigorous shoots ; these, 

 when observed under a bell-glass, were on some days quite sta- 

 tionary, and on other clays moved to and fro only about the 

 eighth of an inch. Consequently the revolving power is here 

 much enfeebled, and under unfavourable circumstances is com- 

 pletely lost. This species must depend on the probable, though 

 not ascertained, spontaneous movements of its leaves, on the 

 rapid growth of its shoots, and on movements from the wind, for 

 coming into contact with surrounding objects: hence, perhaps, 

 it is that the petioles have acquired, as we shall sec, in compen- 

 sation a high degree of sensitiveness. 



The petioles are bowed downwards, and have the same general 

 hook-like form as in C. viticella. The medial petiole and lateral 

 sub-petioles are sensitive, especially the much-bent terminal 

 portion. As the sensitiveness is here greater than in any other 

 species of the genus observed by me, and is in itself remarkable, 

 I -will give fuller details. The petioles, when so young that they 

 have not separated from each other, are not sensitive ; when the 

 lamina of a leaflet has grown to quarter of an inch in length (that 

 is, about one-sixth of its full size), the sensitiveness is highest; 

 but at this period the petioles are much more fully developed pro- 

 portionally than the lamina) of the leaves. Full-grown petioles 

 are not in the least sensitive. A thin stick placed so as to press 

 lightly against a petiole, bearing a leaflet a quarter of an inch in 

 length, caused the petiole to bend in 3 h. 15 m. ; in another case a 

 petiole curled completely round a stick in 12 h. These petioles 



