BOTANY. 19 
when those at the apex are longest. Leaves also are cuneate or wedge- 
shaped (fig. 8) spathulate (fig. 9), subulate ( fig. 10) ; acwminate, or drawn 
out into a point of greater or less extent (fig. 11); mucronate, with the free 
extremity of the midrib projecting from the margin ( fig. 12). 
When the parenchyma is deficient at the apex, so as to form two rounded 
lobes, the leaf is obcordate ; when the deficiency is very slight, it is 
emarginate ; when the apex is‘ merely flattened or slightly indented, the 
leaf is retuse (fig. 13). If the apex appear as if cut off, so that the margin 
is straight or aie angled, the leaf is truncate (fig. 14). A leaf is 
cordate when the petiole enters a base having a rounded emargination 
(fig. 15), and kidney-shaped or reniform when the apex also is rounded 
(fig. 16). When the lobes are prolonged downwards and acutely, the leaf 
is sagittate (fig. 17); hastate, when they proceed at right angles. When 
the veins of leaves spread out in more than one plane, and by the develop- 
ment of parenchyma a succulent leaf is produced, we may have conical, 
ensiform or sword-lke, prismatic, acinaciform or scymeter-shaped (fig. 18), 
and dolabriform or axe-shaped leaves (fiz. 19). The margin of the leaf 
may be wavy, undulated, or crisped, when it is puckered from a superabun- 
dance of cellular tissue. There are numerous other shapes of leaves, 
although these and their binary combinations are the most important ; the 
rest will readily suggest themselves. 
Compound leaves are leaves in which the divisions pass down to the 
midrib, so as to subdivide the leaf into smaller and distinct leaves, called 
leaflets. The midrib or petiole thus appears like a branch with so many 
distinct leaves, each articulated to it. When the compound leaf dies, it is 
generally the primary petiole that falls off, carrying with it all those 
secondary to it. Leaflets, like leaves, may be either sessile or See aes on a 
distinct stem, called a petiolule. 
A feather-veined compound leaf is said to be pinnate ( fig. 20) when each 
one of the primary veins forms the midrib of a leaflet: bipinnate ( Sig. 21) 
when the secondary veins are midribs, and are articulated to the primary ; 
tripinnate or decompound when the tertiary veins stand in the same relation 
to distinct leaflets : a leaf still further divided is supr adecompound. 
When a pinnate leaf has. one pair of leaflets, it is uniyugate ; two. 
byugate ; many pairs, multijugate. When a pinnate leaf ends in a pair of 
pinnee, it is equally or abruptly pinnate (pari-pinnate) : a single terminal 
leaflet furnishes an unequally pinnate (impari-pinnate) leaf. When the 
leaflets are not directly opposite to each other, the leaf is alternately 
pinnate: it is impari-pinnate when the pinn are of unequal size. 
In leaves with radiating venation, and in which each vein forms the 
midrib of a separate leaflet, we have a fennate leaf with three leaflets : 
quaternate with four; quimate with five, &c. Should the parenchyma 
connecting three ribs of a ternate leaf subdivide, so that each of these forms 
the midrib of a new leaflet, the compound leaf is biternate ; another such 
subdivision gives a ¢reternate leaf, &c. 
The petiole, or that part of the leaf which unites the blade with the stem, 
consists of one or more bundles of vascular tissue, with a varying amount 
19 
