3. Division Spermatophyta

This division comprises all the seed bearing plants. They are familiar green plants which produce seeds through flowers or cones.

General characteristics

• The plant has roots, stems, leaves and seed bearing structures
• They produce seeds
• They have chlorophyll hence photosynthetic
• They have vascular tissue is highly developed with xylem tissue consisting of both xylem tissue and tracheids.

The division spermatophyte consists of two main subdivisions:

1. Gymnospermatophyta
2. Angiospermatophyta.

1. Gymnospermatophyta

Characteristics

• They bear cones of two types, male and female
• After fertilization seeds are not enclosed in a fruit wall.
• They show some xerophytic characteristics such as rolled leaves, needle-shaped leaves, sunken stomata and thick waxy leaves
• Xylem consists mainly tracheids while phloem does not have companion cells.

This subdiviosn has three main classes

Class Coniferales

They include all the common gymnosperms naturally found in areas with little water.

• They have needle-like shaped leaves with a thick waxy cuticle
• Mature naked seeds occur at bases of female cones some months after pollination

Class Cycadales

Cycadeles resemble palms superficially.

• They have long compound leaves which are clustered at the apex of a thick ussualy short and unbranched stems.
• They have cones which are borne at the apex of the trunk among leaves.

Class Ginkgoales

Members of this class are very rare. They have deciduous with fan-like leaves. Examples include Ginkgo biloba species in china

2. Angiospermatophyta.

This is the most advanced group found almost everywhere. They include grasses, herbs, shrubs and trees.

Characteristics

• They are flower bearing and are usually bisexual.
• Seeds are enclosed in an ovary which develops into a fruit.
• Xylem has tracheids and vessels while phloem has companion cells.
• They exhibit double fertilization.

This group is divided into Two Classes

a) Class Dicotyledonae

• These are plant whose embryo of seeds has two cotyledons.
• Their leaves are broad and have networks of veins
• Cross section of stems reveals vascular bundles arranged in rings
• They have taproot system
• Centrally placed star-shaped xylem with phloem alternating with arms of the xylem
• Their flowers have floral parts in five or fours

Examples are herbs, shrubs, and trees. The herbs include plants with all stems such as beans, cabbages, tomatoes and black jack while the shrubs include plants with fairly thick stems such as coffee, tea and cocoa

b) Class Monocotyledonae

• Their seeds have an embryo with one cotyledon
• Relatively narrow leaves with parallel veins
• The cross section of the stem reveals scattered vascular veins
• No vascular cambium hence no secondary growth
• They bear floral parts in threes

Examples include Maize, grass, wheat, sorghum, sugarcane, coconuts, bananas and sisal.