1v = INTRODUCTION TO BOTANY. 
’ 
Branches are 
trichotomous, when the forks are 3-pronged, and this repeated ; 
umbellate, when divided at the apex inte several branches, and the central one 
not larger than the rest. 
82. The straw-like stems.of grasses and some other endogens are often called 
~  §5. The Leaves. 
33. Leaves are expansions which issue laterally from the stem and branches, and 
ae bear a leafbud (29) in their axil, 7.e., the angle formed by the leaf and the 
bran 
34, An ordinary leaf consists of an expanded, usually flat, blade or lamina, joined 
to the stem by a foot-stalk or petiole. The extremity of the lamina next the stem is 
the base, the opposite extremity the apex, and a line separating the upper and under 
surfaces, the margin. ; 
35. Leaves are 
sessile, when the blade rests on the stem without the intervention of a petiole ; 
amplexicaul, or stem-claspiug, when the sessile base of the blade is not a mere 
point, but forms more or less of a ring, clasping the stem horizontally. 
perfoliate, when the base of the blade not only clasps the stem. but closes 
round it on the opposite side, so that the stem appears to pierce through 
the membrane of the leaf itself. 
decurrent, when the edges of the leaf are continued down the stem, so as to 
form raised lines, or narrow stem-borders called wings. : 
sheathing, when the base of the blade, or of the expanded petiole, forms a ver- 
tical sheath round the stem for some distance above the node. 
36. Leaves (and flowers) are called radical, when they spring directly from a rhi- 
zome or stock, or are inserted so close to the base of a stem as to appear to spring 
from the root or stock. Leaves are cauline, when they spring from the main por- 
tions of the stem, and rameal, when from a branch. 
87. Radical-leaves are rosulate, when they spread in a circle on the ground ; cau- 
line or rameal-leaves are fascicled or tufted, when the leaves of two or more nodes are 
brought close together into a pencil-like tuft, by the non-development of the inter- 
nodes ; as in Aspalathus, Asparagus, &c. 
38. Leaves are 
simple and entire, when the blade consists of a single piece, and the margin is 
nowhere indented ; simple being used as the opposite to compound, and 
entire as the opposite to dentate, lobed, or divided. 
ciliate, when bordered with straight hairs, or minute, hair-like teeth. 
dentate or toothed, when the margin is slightly notched at regular distances 
into what have been compared to teeth. Such leaves are serrate when 
the teeth are pointed like those of a saw; crenate, when blunt and 
rounded. The diminutives serrulate, crenulate are used to express 
minutely-serrate, or minutely-crenate. The hollows between the teeth 
age respectively called serratures and crenatures. 
sinuate, when the margin is bluntly indented, with broad, shallow and irre- 
gular hollows between the projections (like the bays between the head- 
lands of a coast) ; wavy or undulate, when the edges of such a leaf are not 
_ flat, but bent up and down (like the waves of the sea). The hollows 
between the projectors are called sinuses. 
lobed or cleft, when more deeply indented or divided, but so that the incisions 
do not reach the midrib or petiole. The teeth or sections of such leaves 
are called lobes. 
divided, when the incisions reach the midrib or petiole, but the parts so di- 
vided off, called segments, do not separate from the petiole, even when 
the leaf falls without tearing. 
compound, when divided to the midrib or petiole, and the parts so divided off, 
called leaflets, bs oboe at least on the fall of the leaf, from the petiole, 
as the whole leaf does from the stem, without tearing. The petiole of a 
compound-leaf is sometimes called the common-petiole (because common 
to all the leaflets, which often are united to it by petiolules or individual 
ope sometimes the rachis, a term also applied to the inflorescence 
