66 CJiapters in Modem Botany chap. 



but forming cables which do not easily snap. " I have," 

 Darwin says, "more than once gone on purpose during 

 a gale to watch a Bryony growing in an exposed hedge, 

 with its tendrils attached to the surrounding bushes ; 

 and as the thick and thin branches were tossed to and 

 fro by the wind, the tendrils, had they not been excessively 

 elastic, would instantly have been torn off and the plant 

 thrown prostrate. But as it was, the Bryony safely rode 

 out the gale, like a ship with two anchors down, and with 

 a long range of cable ahead to serve as a spring as she 

 surges to the storm." 



As to the more precise nature of the movement, it is 

 enough in the meantime to notice that the whole tendril 

 — excepting the base and the tip — is continuously curved, 

 bending in succession to each point of the compass. On 

 a thick tendril a line of paint may be drawn ; this line, if 

 drawn on the surface which chanced to be convex at the 

 time, would first become lateral, then concave, then lateral, 

 and finally convex as at first. 



But we should also give some illustration of the great 

 sensitiveness of tendrils. To those of the passion-flower 

 {Passiflo7'a gracilis) Darwin gave the highest place. "A 

 bit of platinum wire — j of a grain in weight, gently 

 placed on the concave point, caused a tendril to become 

 hooked, as did a loop of soft, thin, cotton thread J^- of a 

 grain. With the tendrils of several other plants, loops 

 weighing Jg- of a grain sufficed. The point of a tendril 

 of Passijiora gracilis began to move distinctly in 25 

 seconds after a touch, and in many cases after 30 

 seconds." 



Summary. — To sum up after Darwin : the first action of 

 a tendril is to place itself in a proper position ; if a twining 

 plant or a tendril gets by any accident into an inclined posi- 

 tion, it soon bends upwards, though secluded from the light. 



