LEAVES FORM AND POSITION 



77 



FIG. 99. CLASP- 

 ING LEAF OF A 

 WILD ASTER. 



The same is said of flowers and fruits. 

 The blade of a sessile leaf may partly or 

 wholly surround the stem, when it is said 

 to be clasping. Examples : aster (Fig. 99), 

 corn. In some cases the leaf runs down 

 the stem, forming a wing ; such leaves are 

 said to be decurrent (Fig. 100). When 

 opposite sessile leaves are joined by their 

 bases, they are said to be connate (Fig. 101). 

 Leaflets may have one or all of these 



three parts, but the stalks of 

 leaflets are called petiolules 

 and the stipules of leaflets are 

 called stipels. The leaf of the 

 garden bean has leaflets, peti- 

 olules, and stipels. 



The blade is usually attached 

 to the petiole by its lower edge. 

 In pinnate-veined leaves, the petiole seems to 

 continue through the leaf as a midrib (Fig. 91). 

 In some plants, however, the petiole joins 

 the blade inside or beyond the margin (Fig. 92). Such 

 leaves are said to be pel- 

 tate or shield-shaped. This 

 mode of attachment is par- 

 ticularly common in float- 

 ing leaves (e.g. the water 

 lilies). Peltate leaves are 

 usually digitate-veined. 



How to Tell a Leaf. It 

 is often difficult to distin- 



guishcompound leavesfrom ^ , OI ,_ Tvlo PAIRS OF CoNNATE 

 leafy branches, and leaflets LEAVES OF HONEYSUCKLE. 



FIG. ioo. DE- 

 CURRENT 

 LEAVES OF 

 MULLEIN. 



