208 PRACTICAL LESSONS IN SCIENCE. 



are: linear, when the leaf is several times longer than wide 

 and of the same width throughout; lanceolate, when sev- 

 eral times longer than wide and tapering upwards and down- 

 wards from the lower third of the leaf; oblong, when two or 

 three times as long as broad with rounded base and apex ; 

 elliptical and oval, much the same as oblong but taper- 

 ing more toward the ends of the leaf; ovate, when the out- 

 line is like the lengthwise section of a hen's egg, the broader end 

 downward; orbicular, when nearly circular in outline. When 

 the leaf tapers toward the base it may be oblanceolate, spatu- 

 late, obovate, or wedge-shaped. 



If we consider the base of the leaf it may be cordate, or heart- 

 shaped, reniform or kidney-shaped, auriculate or eared, sagi- 

 tate or arrow-shaped, and hastate or halberd-shaped. The leaf 

 of the water-lily and mandrake are peltate or shield-shaped. 



When the apex of the leaf is considered it may be acuminate 

 or pointed, acute or obtuse; truncate, when the end appears as if 

 cut off square ; retuse, when the rounded summit is slightly in- 

 dented; emarginate, when the summit is decidedly notched; 

 obcordate, when the apex is heart-shaped; cuspidate, when 

 tipped with a sharp rigid point ; aristate, when the apex is like 

 a bristle. 



Leaves also vary in outline. When the margin is an even line 

 without teeth or notches the leaf is entire. It is serrate or saw- 

 toothed when the margin is cut into sharp teeth pointing to ward 

 the apex of the leaf. Dentate, when the teeth are wider and point 

 outward; crenate, when the teeth are rounded; repand or 

 wavy; sinuate, like repand with deeper waves; incisid, when 

 the margin is cut into sharp, deep and irregular teeth. 



When the incisions do not extend more than halfway to the 

 midrib, dividing the leaf into a definite number of somewhat 

 rounded parts, it is said to be lobed, and the divisions are called 

 lobes, and their number is expressed by the phrase three-lobed, 

 five-lobed, etc. If the divisions extend more than halfway to the 

 midrib, the leaf is said to be cleft, and it may be three-cleft or five- 

 cleft, etc. If the incisions go nearly to the midrib or base of the 



