OF LEAVES. 79 
or entirely surround the stem, when they are said to be amplexical 
or semiamplexical. The leaf is simple when the limb consists of 
one piece either quite entire or variously indented, cleft or divided 
on the edge; and compound when it consists of one or more 
leaflets, each of which is jointed to the common petiole by inter- 
mediate little petioles, sometimes very short, and said to be petio- 
lated. The leaf of the Lime-tree (Tilia), Fig. 97, is simple; that 
of the Robinia, or False Ac- 
cacia, Fig. 98, is compound. 
It happens sometimes that 
the petiole is branching’ and 
bears petioles of the second or 
third order, upon which are 
inserted petiolules with their 
folioles. This occurs in Gle- 
ditschia tricanthus, Fig. 99, a } 
highly ornamental group of Sy//> 
trees, with branching thorns in © ~ 
some of the species. When \} 
the division of leaves is carried 
further, the term decompound 
is made use of; the Hemlock 
(Conium maculatum), is said to 
be su upra-decompound. The 
limb of the leaf isoften continued | 
all round, and sufficiently large | 
to embrace it, as we see in the | 
Box-tree, the Iris, and some | 
other plants. The edge of the : 
limb of the leaf is generally Fig. 97.—Leaf of the Lime-tree. 
more or less serrated ; according to the form and depth of these 
inequalities round the margin, the leaf is said to be dentate, 
crenale, serrate, lobed, and cloven. 
Leaves are dentate when the edge is intersected with acute, 
Pointed teeth, as in the Chestnut, Fi ig. 100. Crenate when the 
Margin presents sail/ant parts, as in the Saxifrage, Fig. 101. They 
ate lobed when the leaf is more deeply indented, as in the Gingho, 
Fig. 102, They are cleft when their division embraces one half of 
