XVl] PARASITES, CLIMBERS, ETC. 129 



pulvinus. Consequently they are termed stipular spines 

 and pulvinar spines respectively. 



In the common Barberry the case is again somewhat 

 different in detail. As before, we find buds in the axils 

 of the triple or otherwise branched spines, but careful 

 comparison shows that the spines are themselves repre- 

 sentative of a whole leaf, and if we pull off the triplet 

 of spines we find that they run down to a common leaf- 

 base, leaving a scar similar to that left by ordinary leaves. 

 Here, then, the spines are leaf-spines. 



With regard to other complications of the twigs and 

 branches, they are dealt with in detail in a subsequent 

 section of the book, and it suffices to state here that only 

 very few of the extraordinarily numerous varieties of 

 parasitic plants, e.g. Mistletoe, of twining plants, e.g. 

 Honeysuckles, of tendril-climbers, e.g. Clematis, Vine and 

 Virginian Creeper, and of root-climbers, e.g. Ivy, come 

 within the scope of the present scheme. 



The parasite is known at once by its being rooted 

 in the tissues of some totally different plant. 



The root-climber is known by the dense masses of pale 

 short roots put out from that part of its stem which is 

 turned away from the light and which adjoins the wall, 

 tree-trunk, or other support, up which it (Ivy) is growing. 



The twining Honeysuckles wind their stems round 

 other stems and branches, and occasionally round some of 

 their own. 



The tendril-climbers here concerned exhibit examples of 

 two chief classes of these remarkable plants. In Clematis 

 the tendrils are seen to be leaf-structures even in winter, 

 because they bear buds in their axils. But the tendrils 

 of the Vine and the Virginian Creeper are obviously not 

 leaves, partly because they do not bear buds in their 

 axils, but also because they arise in the wrong place for a 



w. I. 9 



