io8 



OUTLINES OF PLANT LIFE. 



in form to protect the inner ones, and to facilitate the visits 

 of insects {s, p, fig. 66). A shoot whose leaves are thus 

 clustered and specialized constitutes a "flower." The 

 leaves adjacent to the flower leaves are also more or less 

 modified in form and reduced in size. 

 They are called bracts {h ''^'3> fig. po). 



135. (5) Storage leaves. — Other 

 leaves are utilized for purposes of stor- 

 age. For this purpose the ribs are re- 

 duced in number and size, while the BBi*'j( 

 softer tissues of the leaf are often 



FrG. 102. Fig. 103 



Fig. T02. — 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 toliage 



About half natural size. — After Frank. 

 Fig. 103.— Piece of the stem of locust {Robinia Pseudacacia), showing stipules in the 



form of thorns. Natural size.— After Kerner. 



enormously developed, and serve as the receptacles of 

 the reserve food. The primary leaves of the seed plants 

 (cotyledons) are often much distorted by the deposit in them 

 of reserve food for the embryo. When such leaves possess 

 sheathing bases the structure resulting from the union of a 

 number of such leaves upon a short axis is called a bulb. 



