Fig. 84. 



An auriculate leaf. 



A perfoliate leaf. 



Connate leaves. 



Fig. 87. 



Another character relating to the base is the 

 mode of attachment of the blade to the petiole. 

 Usually the midrib, or set of primary ribs of the 

 blade, is in a direct line with the petiole ; but some- 

 times the ribs, as they pass from the petiole into the 

 blade, separate and radiate horizontally from the top 

 of the stalk, so that the latter appears to be inserted 

 into the back of the leaf ; such a condition is called 

 peltate, and occurs in Tropceolum ma/us and other 

 plants with orbicular leaves (fig. 87). 



ApeX Of the Leaf. The apex Or point of the leaf A peltate orbicular leaf. 



has certain characters: it may be acute, or sharp 

 (tig. 66) ; acuminate, or with the point drawn out gradually Fig. 88, 

 (fig. 68), or abruptly (fig. 78) j or mucronate, when it is tipped 

 with a spine (fig. 88). It may also be obtu.se, when an ordi- 

 narily pointed form is suddenly rounded off at the tip ; emar- 

 ginate, when there is a shallow notch where the point should 

 be ; retuse, when a notch of this kind is deep : this last form 

 approaches to the obcordate (fig. 108). 



Margin of the Leaf. The margins of the leaf are either 

 entire, that is, with an unbroken edge (fig. 71) ; crenate, when 

 they exhibit a series of small rounded teeth or scallops 

 (fig. 79) ; dentate when the teeth are acute and pointed ra- nate leaf, 

 dially (fig. 73) ; serrate, when sharp teeth point towards 

 the apex (fig. 83) ; retroserrate, when sharp teeth point towards the base. 

 If there are coarse teeth, the margins of which are again more finely 

 toothed, as in the Elm, the leaves are doubly serrate (or doubly dentate). 

 Sometimes it is requisite to say, irregularly toothed, or incised, as in many 

 Thistles ; and these teeth, as well as those of regularly dentate or serrate 

 leaves, may be tipped with spines, when they are termed spinose-serrate, 

 &c. When the outline exhibits shallow wavy curves, it is sometimes 

 called repand (figs. 86 & 87). The margin may also be revolute, or rolled 

 back toward the lower face (fig. 75), or involute when rolled round on to 

 the upper surface. Sometimes, through excessive growth of the marginal 

 parenchyma, the edges of the leaf are undulated (as when the edge of a 

 strip of paper swells from being wetted (fig. 95)). 



