CONIFERS

They can bear seed in distinctive cones. First time they appeared in the fossil record in the Permian period over 200 million years ago, and they are still abundant today.

There are seven families of living conifers, containing over 600 species. They are widely distributed, dominating forest habitats in the earth's colder, drier regions which other trees cannot survive.

The leaves of conifers vary widely. Conifer leaves are usually covered in a waxy layer, and the stomata (tiny pores) lie beneath the leaf surface. These leaf characteristics prevent water loss and help conifers resist drought. In most conifers, the leaves develop on long shoots and are arranged spirally and alternately. 

Conifers produce distinct male and female cones on the same or separate trees.

These function as flowers. Female cones tend to be much larger than males.  Male conifer flowers may appear in the leaf axils or on new shoots. They usually wither away after the pollinating period has ended.

Male and female cones

Conifers are wind-pollinated. After pollination, the scales of the female cone close tightly, until the developed seeds are released from the mature cones (now serving as the fruit). In the “closed-cone pines,” the heat produced by a forest fire is usually needed to liberate the seeds. The Taxaceae (yew family) do not have cones: each seed is enclosed in a fleshy coating, known as an aril.

 

Conifers are known for attaining enormous heights. Giants of the conifer world include giant sequoia (Sequoiadendron giganteum), and the grand fir (Abies grandis), which may reach a height of 200 ft (60 m). 

Sequoiadendron giganteum