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is familiarly known, there is at least one neutral point in 

 a caught and coiled -up tendril, usually in the middle, the 

 turns on one side of it running from right to left, on the other 

 side from left to right. That the coils, whether simple or 

 double and reversed (as the case may be), are not determined 

 by any peculiarity in the tendril, but merely by the relative 

 shortening of one side, may be readily shown by a thread cut 

 from a piece of india-rubber, of unequal tension of the two 

 sides ; this, when stretched and allowed to shorten while the 

 two ends are held fast in the same plane, forms at once a pair 

 of reverse coils, or three or four such coils, just as caught 

 tendrils do. 



Mr. Darwin explains the point by analogous practical illus- 

 trations, lie shows, moreover, that an important service ren- 

 dered by the coiling or spiral contraction " is that the tendrils 

 are thus made highly elastic." In the Virginia Creeper, where 

 the ends of the compound tendrils are peculiarly attached, 

 " the strain is thus equally distributed to the several attached 

 branches of a branched tendril ; and this must render the 

 whole tendril far stronger, as branch after branch cannot sep- 

 arately break. It is this elasticity which saves both simple 

 and branched tendrils from being torn away during stormy 

 weather. I have 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 or thin branches were tossed to and fro by the wind, the 

 attached tendrils, had they not been excessively elastic, would 

 have been instantly 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 a long range of cable ahead, to 

 serve as a spring as she surges to the storm." 



Moreover, while unattached tendrils soon shrink up or 

 wither and fall off, as we observe in the Grapevine, Virginia 

 Creeper, etc., these same plants show how an attached tendril 

 thickens and hardens, gaining wonderfully in strength and 

 durability. In a Virginia Creeper, " one single lateral branch- 

 let of a (dead) tendril, estimated to be at least ten years old, 

 was still elastic and supported a weight of exactly two pounds. 



