i 3 o 



PLANT LIFE. 



158. (i) Tendrils. — The leaf blade alone, or some of its 

 branches, or the petiole and blade, may develop as a cylin- 

 drical body, without wings and sensi- 

 tive, known as a tendril. In the pea, 

 the stipules become very large, and 

 take the function of the reduced blade 

 (fig. 156). In other plants the base 

 may be broadly winged for the same 

 purpose. 



Fig. 156. — Portion of shoot of pea, with a pinnately compound leaf whose upper leaflets 

 are modified into tendrils and the stipules greatly developed to serve as foliage. 

 About half natural size. — After Frank. 



Fig. 157. — Piece of the stem of locust {Robinia Pseudacacia), showing stipules in the 

 form of thorns. Natural size. — After Kerner. 



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

 conical and sharp-pointed thorns or spines, either branched 

 or unbranched (fig. 390). Sometimes the stipules alone 

 become thorns, as in locust and acacia (fig. 157). Neither 

 tendrils nor thorns can be distinguished structurally • from 

 similar forms of the shoot. 



160. (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. 101, 102, 105, 109, 138, 139, 



