356 A TEXT-BOOK OF BOTANY. 



obcordate. Sometimes the apex appears like the continuation of 

 the midrib, when it is termed cuspidate or mucronate. 



Base of Leaf. — Some of the terms used in describing the gen- 

 eral outline, as well as the apex of the leaf, are also applied to the 

 base, as obtuse, truncate, cordate, reniform, etc. Other terms, 

 however, especially apply to the base, as cuneate or wedge- 

 shaped ; connate-perfoliate, 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 frequently 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, whcu the divisious 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 lobes are 

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

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

 205), 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 compound' leaf. The distinction 

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

 the axil. The diflference 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 off individually. Com- 

 pound leaves may be divided into PiNNATELY-compound (Fig. 204) 

 or PALMATELY-compound (Fig. 210, 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. 207) the leaf is said to be 



