114 BOTANY AND PHARMACOGNOSY. 



shaped; connate-perfoliatEj when opposite leaves are con- 

 nected at the base and surround the stem; perfoliate, when the 

 leaf simply clasps the stem. In Monocotyledons the base of the 

 leaf is frecjuently developed as a closed or open sheath, some- 

 times provided with a membranous protuberance between the 

 sheath and the blade, as in the ligule of grasses and sedges. 



Margin of Leaf. The leaves of many woody dicotyledonous 

 plants of temperate regions possess an even margin. The others 

 according to the degree and character of the incisions or inden- 

 tations, are described as serrate, when the apex of the divisions 

 or teeth is sharp and directed forward like the teeth of a saw ; 

 dentate, when the divisions project outward; crenate, when 

 the teeth are more or less rounded ; repand, when the margin is 

 somewhat wavy ; sinuate, when the wavy character is pro- 

 nounced ; LOBED, when the incisions extend not more than half- 

 way into the lamina, and the sinus (or hollow) and the lobe are 

 more or less rounded ; cleft, when the incisions are still deeper 

 and the sinuses and lobes are somewhat acute ; and divided (Figs. 

 75 and 76), when the incisions extend almost to the midrib. 



Compound Leaves, The divisions of a parted leaf may 

 assume the form of a simple leaf, when the divisions are known 

 as leaflets and the whole as a compovmd leaf. The distinction 

 between a simple leaf and a leaflet is, that the former has a bud in 

 the axil. The difference between the divisions of a simple leaf 

 and those of a compound leaf is this, in the former they never 

 become detached from the petiole or midrib, whereas in the com- 

 pound leaf they are articulated and drop oft' individually. Com- 

 pound leaves may be divided into PiNNATELY-compound (Fig. 74) 

 or p.\LMATELY-compound (Fig. 78, E), this distinction depend- 

 ing upon whether the leaflets are arranged pinnately or palmately. 

 A number of forms of pinnately-compound leaves are recognized. 

 When the leaflets are all lateral (Fig. 71) the leaf is said to be 

 PARI-PINNATE ; when there is an odd or terminal leaflet as in 

 the locust (Fig. 74) the leaf is impari-pinnate ; when the midrib 

 is prolonged into a tendril as in the garden-pea {Pisimi) the 

 leaf is said to be cirriiiferous-pinn.-\te. 



Movements of Leaves. The leaves as well as other organs 



