70 THE LEAVES. [CHAP, 



on each side of the stem, as in Teazle, the leaves are said 

 to be connate. Sometimes, in sessile leaves, the margins 

 of the blade are continued down the sides of the stem, 

 forming wings to it. Such leaves are decurrent. They 

 are very common amongst Thistles. When the petiole 

 joins the blade upon its under surface and not at the 

 margin, as in Garden Nasturtium (Tropoeoluin), the leaf 

 is said to be peltate. 



The margin of the leaf varies, being sometimes perfectly 

 continuous and not indented or toothed at all, when it is 

 termed entire ; it is serrate if with sharp teeth directed 

 forward, like those of a saw ; dentate if with sharp teeth 

 directed outward ; crenate if with rounded teeth. 



The surface may be more or less hairy, or altogether 

 without hairs, when it is termed glabrous. Different 

 terms are used to denote different kinds and degrees of 

 hairiness, the more important of which are denned in the 

 Glossary at the end of the book. 



12. Taking up again a specimen of the Pea or Bean, 

 observe on each side of the base of the petiole a leafy 

 organ somewhat resembling a leaflet. In the Pea these 

 organs are very large larger indeed than the leaflets. They 

 are relatively very large also in the Garden Pansy. These 

 are the stipules. They originate as lateral appendages of 

 the leaf-base, and usually attain their full development 

 before the leaf to which they belong. Leaves provided 

 with stipules are called stipulate, and leaves destitute of 

 them, as those of Wallflower, exstipulate. Like leaves and 

 leaflets, the stipules vary in form, but they are generally 

 small, and often fall away very early, as in the Oak and 

 Beech. 



13 Foliage-leaves are sometimes curiously modified, 

 either to serve some special purpose, or by the absence of 

 the blade, or the reduction of the leaf to a mere spine. 

 Thus in the Pea we find the extremity of the common 

 petiole and two or more of the lateral leaflets assume the 

 form of tendrils, enabling the weak stem to lay hold of 

 supports in climbing. Compare with the tendrils of the 

 Pea those of the Grape-vine or Virginian Creeper, which 

 we have described as branches modified for the same 

 purpose (page 59). 



In Barberry, the leaves borne by the elongated branches 



