212 VEGETABLE ORGANOGRAPHY'. 



spiny plants. The transformation into tendrils supposes, 

 on the contrary, a soft, flexible, fibrous tissue, capable of 

 elongation; therefore we remark in each family, that 

 those plants, in which the stem has a tendency to be 

 prostrate or climbing, have at the same time and for the 

 same reasons some organs transformed into tendrils. 

 The Vicieae, Mimoseae, PassifloreaD, Sapindaceae, and 

 Smilaceae, with weak stems, have well-developed ten- 

 drils ; whilst in the same groups we find no tendrils, or 

 only rudimentary ones, where the stem is stronger ; 

 thus Orobus and Faba, which have a firm stem, are the 

 only Vicieae which are almost devoid of them ; none of 

 the Mimoseae with strong stems have any, whilst 

 Entada, which has twining stems, is furnished with 

 them ; the arborescent Passifloreae are alone devoid of 

 them ; the weak and climbing Sapindaceae only, as Car- 

 diospermum, Urvillea, Paullinia, are furnished with 

 them ; Smilax herbacea, which has an erect stem, is 

 devoid of them, whilst all the other species are provided 

 with them. Thus it is generally found that tendrils are 

 only developed in plants too weak to support themselves. 

 The existence of this kind of support enables them to 

 twine round trees or shrubs; therefore most plants of 

 this kind live, in preference, in forests when they are 

 very large, and among bushes and hedges when small. 

 The farmer imitates this natural phenomenon when he 

 sows Vetches among Oats, which serve to support them. 

 The twisting of twining stems and tendrils takes 

 place in each species in a determined manner — either 

 crossways or spirally ; the former is performed upon the 

 same plant, and only takes place in tendrils which find 

 no other body to lay hold of: this is frequently seen in 

 Sapindaceae. The twining in a spiral manner, properly 

 so called, always takes place in stems or tendrils which 

 are twisted around a long body. What is most remark- 



