io6 



OUTLINES OF PLANT LIFE. 



may be winged to serve for "foliage, as in Nepenthes (fig. 



220). A few plants have their leaves modified so as to serve 



as traps, which, by their 

 sudden movements, capture 

 small animals (figs. 224, 

 225, 226). 



But generally the foliage 

 function is subordinated to 

 the other work, and the leaf 

 takes on peculiar forms, the 

 more important of which are 

 as follows: 



131. (i) Tendrils.— The 

 leaf blade alone, or some of 



Fig. loo.— Portion o( a plant of the dwarf itS branches, Or the petiolc 

 garden-nasturtium {Tropizolum minus) 



The long petiole a, a. a of the leaf I is and blade, may develop as 



sensitive to contact and has coiled about , . . . , . , 



the support and its own stem, ji. z, axil- a Cylindrical body, Without 



lary branch. Natural size. — After Sachs . ... 



Wings and sensitive, known 

 as a tendril. In the pea, the stipules become very large, 

 and take the function of the reduced blade (fig. 102). In 

 other plants the base may be broadly winged tor the same 

 purpose. 



132. (2) Thorns. — The leaves may develop into slender 

 conical and sharp-pointed thorns or spines, either branched 

 or unbranched (fig. 228). Sometimes the stipules alone 

 become thorns, as in locust and acacia (fig. 103). Neither 

 tendrils nor thorns can be distinguished structurally from 

 similar forms of the shoot. 



133. (3) Scales. — In buds, on underground stems and on 

 various parts of the aerial stem, are found small, scale-like 

 leaves of various shapes (figs. 63, 64, 67, 71, 89, 90, 198). 

 These scales may represent the sheathing base only; they 

 may be the base with the stipules (fig. 90) ; or they may 

 represent the leaf base and the blade. The petiole in all 



