FORMS OF SIMPLE LEAVES. 



77 



slightly depressed (fig. 157), the leaf is refuse (retusus, blunt) ; and 

 when the apex ends abruptly in a straight margin, as in the Tulip 

 tree (fig. 163), the leaf is 

 truncate. When the vena- 

 tion is prolonged down- 

 wards at an obtuse angle 

 with the midrib, and round- 

 ed globes are formed, as in 

 Dog-violet, the leaf is cor- 

 date or heart-shaped (fig. 

 153), or kidney-shaped (reniform} when the apex is rounded (fig. 

 161), as in Asanun. When the lobes are prolonged downwards 

 and acute (fig. 165), the leaf is sagittate (sagitta, an arrow); when 

 they proceed at right angles, as in Eumex Acetosella, the leaf is hastate 

 (hasta, a halbert) or halbert-shaped. When a simple leaf is divided 

 at the base into two leaf-like appendages (fig. 169), it is called auricu- 

 late (auricula, the ear). When the veins spread out in various planes, 

 and there is a large development of cellular tissue, so as to produce a 

 succulent leaf, such forms occur as conical, prismatical, ensiform or 

 sword-like (ensis, a sword), acinaciform (acinaces, a scimitar) or scimitar- 

 shaped (fig. 172), and dolabrifoi~m (dolabra, an axe) or axe-shaped 

 (fig. 171). When the development of cells is such that they more than 

 fill up the spaces between the veins, the margins become wavy, crisp, 



164 



165 



or undulated, as in Rumex crispus and Eheum undulatum (fig. 1 74). 

 By cultivation the cellular tissue is often much increased, giving rise 

 to the curled leaves of Greens, Savoys, Cresses, Lettuce, &c. 



151. Compound Leaves are those in which the divisions extend to 



Fig. 161. Reniform or kidney-shaped entire leaf of Asarum. Radiating venation. 



Fig. 102. Elliptical and somewhat lanceolate leaf; three-ribbed. 



Fig. 163. Three-lobed, truncate, or abrupt leaf of Liriodendron tnlipifera. 



Fig. 164. Rounded entire leaf, ending in a short point 



Fig. 165. Sagittate or arrow-shaped leaf of Sagittaria. 



Fig. 166. Lanceolate, acute leaf, with minute teeth or dentations at the margin. 



Fig. 167. Subulate or awl-shaped leaf. 



Fig. 168. Whorl or verticil of linear-obovate leaves. 



Fig. 169. Auriculate lanceolate leaf, oblique at the base, with minute toothings at the margin. 



