BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

X. SEED PLANTS

Division Flowering Plants (Magnoliophyta)

Flowering plants comprise about 250,000 plant species and are divided into two classes: dicotyledons and monocotyledons.

Class Magnoliopsida, Dicotyledons (Magnoliopsida, Dicotyledones)

The following subclasses of dicotyledons are distinguished: Magnoliidae, Ranunculidae, Caryophyllidae, Hamamelididae, Dilleniidae, Rosidae, Lamiidae, Asteridae.

This class includes plants with the following characteristics: the seed embryo has two cotyledons, sometimes one, rarely three or four. The cotyledons are lateral (side-positioned), with three vascular bundles in each. The ROOT System is taproot, which develops because the primary (embryonic) radicle grows into a main root. Leaves have a distinct petiole and diverse Structure: they are often

dissected and compound, and may have sheaths and stipules, usually two in number. Venation is pinnately or palmately reticulate (rarer arcuate or parallel). The Vascular System of the stem consists of a single ring of vascular bundles, typically with cambium. The phloem contains parenchyma. The stem cortex and pith are optimally differentiated. Flowers are most commonly pentacyclic or tetracyclic, 5- or 4-merous, and only in some (mostly primitive ones) are they 3-merous.

Dicotyledons are represented by A wide variety of woody and herbaceous plant forms and grow in diverse ecological conditions. The class encompasses eight subclasses, 429 families, about 10,000 genera, and over 190,000 species.