78 



FOKMS OF COMPOUND LEAVES. 



the midrib, or petiole (fig. 175), and receive the name of foliola or 

 leaflets. The midrib, or petiole, has thus the appearance of a branch 



170 171 172 173 174 



with separate leaves attached to it, but it is considered properly as 

 one leaf, because in its earliest state it arises from the axis as a single 

 piece, and its subsequent divisions in the form of leaflets are all in 

 one plane. When a compound leaf dies, it usually separates as one 

 piece. The leaflets are either sessile (fig. 176), or have stalks, called 



petiolules (fig. 175), according as the vascular bundles of the veins 

 spread out or divaricate at once, or remain united for a certain length. 



Fig. 170. Pedate or pedatifid leaf of Hellebore. Radiating venation. 



Fig. 171. Dolabriform or axe-shaped fleshy succulent leaf. Hidden-veined. 



Fig. 172. Acinaciform or scimitar-shaped succulent leaf. Hidden-veined. 



Fig. 173. Oval leaf with converging veins ; not reticulated. 



Fig. 174. Palmately-lpbed leaf, crisp or undulated at the margin. Radiating venation. 



Fig. 175. Leaf of Robinia pseudo-acacia, often called Acacia. The leaf is impari-pinnate, or 

 alternately pinnate. The pinna are supported on stalks or petiolules. p, Petiole or leaf-stalk. 

 I, Lamina or blade divided into separate leaflets or pinnae. 



Fig. 176. Septenate leaf of jEsculus Hippocastanum or Horse Chestnut, p, Petiole. I, Lamina, 

 divided into seven separate leaflets. 



