iod APPENDAGES. 



in distributing the vegetable kingdom into natural or- 

 ders, has frequently derived from them his secondary 

 characters. 



In their functions these organs are auxiliary to the 

 leaves, serving like them for the elaboration of the sap ; 

 and in some of the Pea vines it has been observed that 

 the latter occasionally disappear, leaving only the sti- 

 pules to supply their place. 



3. TENDRILS. 



These are filiform appendages by which weak stems 

 .ire attached to their supporters. They usually arise 

 from the branches, being opposite to the leaves in the 

 Vine, and axillary in the Passion flower. In a few in- 

 stances they arise from the leaf, and very rarely from 

 the petiole and flower stalk. In the Traveller's Joy, 

 Clematis Virginica, the petiole itself performs the of- 

 fice of tendrils, and twines like them around other ob- 

 jects for support, and in the Annona hexapetala, the 

 flower stalk forms a hook and grasps the neighbouring 

 branches serving to suspend its very heavy fruit. The 

 young tendril usually proceeds in a straight direction 

 till it has found something to cling to, after which it as- 

 sumes its spiral form and brings the young vine closer 

 to the objects which sustain it. Some turn from right 

 to left, some from left to right, while a few possess the 

 property of twining in either direction. In the Ivy, 

 Fig. 18, they are not spiral, being merely fibres which 

 arise from the stem and penetrate the bark of the 

 neighbouring trees, or if denied access to other vege- 

 tables they cling to the naked wall, " attaching them- 

 selves firmly as the stem elongates, which thus often 

 climbs to the summit of the loftiest trees or to the bat- 



