IBi TENDEIL-BEAKEES. Chap. IV, 



still furtlier secured by the spiral folds, as I have seen 

 with Passiflora quadrangularis ; but this action is of 

 little importance. 



A far more important service rendered by the spiral 

 contraction of the tendrils is that they are thus made 

 highly elastic. As before remarked under Ampelopsis, 

 the strain is thus^ distributed equally between the 

 several attached branches ; and this renders the whole 

 far stronger than it otherwise would be, as the branches 

 cannot break separately. It is this elasticity which pro- 

 tects both branched and simple tendrils from being torn 

 away from their supports 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 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. 



When an unattached tendril contracts spirally, the 

 spire always runs in the same direction from tip to 

 base. A tendril, on the other hand, which has caught 

 a support by its extremity, although the same side is 

 concave from end to end, invariably becomes twisted 

 in one part in one direction, and in another part in the 

 opposite direction ; the oppositely turned spires being 

 Eepeurated by a short straight portion. This curious 



