Page 9 - Tài liệu Ebook cây cảnh Bonsai Basics

HOW TREES GROW 11

Leaves may vary according to species The needle-like leaf is a good example
and variety; they may be simple (the oak of the way in which the leaf has adapted
leaf, for example), multiple and com- to a dry, cold or hot climate, by restrict-
pound (like the horse chestnut); they ing transpiration. Because a needle lasts
may be regular in shape, dentate or for several years, the tree is released from
linear, ovate, lanceolate or cuneate, etc. the burden of forming a complete set of
A conifer needle is very simple in new leaves every year. But it should be
structure. Its main characteristic is its noted that the needle's permanence is
narrow, elongated shape tapering to a only relative, since they also eventually
point (hence the name). Unlike a leaf fall from the tree: a look under the
blade of a typical broad-leaved tree nearest conifer will confirm this.
which is generally very thin, the needle Once fallen, all leaves start to decom-
is fleshy and thick, making it very pose and help to form humus. In this
resilient. But like leaves, needles also way, some of the minerals drawn up by
provide for photosynthesis. the roots are returned to the soil.

Conifers

conical umbrella columnar

Broad-leaved trees

domed crown fastigiate ball-shaped weeping