62 MR* DAUWTK ON CLIMBING PLANTS. 



circular sweeps, against the sun, eacli in 1 h. 15 m., and two others 

 in 1 h. 20 m. and 1 h. 23 m. Sometimes it travels in a much in- 

 clined position, and sometimes nearly upright. The lower part 

 moves hut little, and the basal portion or petiole, which bears the 

 leaflets, not at all ; nor do the internodes revolve ; so that here we 

 have the tendril alone moving. With most of the species of 

 Signonia and with EccrernocaTyus, the internodes, tendrils, and 

 petioles all revolve. The long, straight, tapering main stem of the 

 tendril of the Cohcea bears alternate branches ; and each branch is 

 several times divided, with the finer branches as thin as very thin 

 bristles, extremely flexible, so that they are blown about by a 

 breath of air, yet strong and highly elastic. The extremity of 

 each branch is a little flattened, and terminates in a minute double 

 (but sometimes single) hook, formed of hard, transparent, woody 

 substance, and as sharp as the finest needle. On the eleven-inch 

 tendril I counted ninety-four of these beautifully constructed 

 little hooks. They readily catch soft wood, or gloves, or the skin 

 of the hands. Excepting these hardened hooks, and excepting 

 the basal part of the central stem of the tendril, every part of 

 every branch is highly sensitive on all sides to a slight touch, and 

 bends in a few minutes towards the touched side. By lightly 

 rubbing several branches on different and opposite sides, the whole 

 tendril rapidly assumes an extraordinarily crooked shape : these 

 movements from contact do not interfere w^ith the ordinary re- 

 volving movement. The branches, after becoming greatly ciu'ved 

 from being touched, straighten themselves at a quicker rate than 

 in almost any other tendril seen by me, namely, in between half 

 an hour and an hour. After the tendril has caught any object, 

 the spiral contraction also begins after an unusually short inters'al 

 of time, namely, in about twelve hours. 



Before the tendril is matui^e, the terminal branches cohere and 

 the hooks are curled closely inwards : at this period no part is sensi- 

 tive to a touch ; but as soon as all the branches have diverged and 

 the hooks stand out, full sensitiveness is acquired. It is a singular 

 circumstance that the immature tendril, before becoming sensitive, 

 begins to revolve at its full velocity : this movement must be use- 

 less, as the tendril in this state can catch nothing : it is a rare 

 instance of a want, though only for a short time, of perfect co- 

 adaptation in the structure and functions of a climbing-plant. 

 The petiole with the tendril perfectly matured, but with the leai- 

 lets still quite small, stands at this period vertically upwards, the 

 young growing shoot or axis being thrown to one side. The ten- 



