Conifers (Gymnosperms)

 

The Gymnosperms are a group of seed-bearing plants that includes

conifers, cycads, Ginkgo and Gnetales. The term "gymnosperm"

comes from the Greek word gymnospermos, meaning "naked

seeds", after the unenclosed condition of their seeds (called ovules

in their unfertilized state). Their naked condition stands in contrast

to the seeds or ovules of flowering plants (angiosperms) which are

enclosed during pollination. Gymnosperm seeds develop either on

the surface of scale- or leaf-like appendages of cones, or at the end

of short stalks (Ginkgo).

 

The gymnosperms and angiosperms together comprise the sperma-

tophytes or seed plants. By far the largest group of living gymno-

sperms are the conifers (pines, cypresses, and relatives), followed

by cycads, Gnetales (Gnetum, Ephedra and Welwitschia), and

Ginkgo (a single living species). There are between 700 and 900

extant or currently living species of
Gymnosperms.

 

It is widely accepted that the Gymnosperms originated in the late
Carboniferous Period. Early characteristics of seed plants were

evident in fossils of the late Devonian period around 380 million

years ago. Conifers are by far the most abundant extant group of

Gymnosperms with six to eight families, with a total of 65-70

genera and 600-630 species (696 accepted names). Conifers are

woody plants and most are evergreens. The leaves of many conifers

are long, thin and needle-like, others species, including most

Cupressaceae and some Podocarpaceae, have flat, triangular scale-

like leaves. Genus Agathis in Family Araucariaceae and Genus

Nageia in Family Podocarpaceae have broad, flat strap-shaped

leaves.

 

Cycads are the next most abundant group of Gymnosperms, with

about 130 species. The other extant groups are the 75 - 80 species

of Gnetales and one species of Ginkgo.

 

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