The the bases of seed cone scales. Each pollen

The name gymnosperms comes from the Greek word: gymnos, meaning naked, and sperma, a seed. The seeds are exposed or “naked”, not enclosed within an ovary. Thus, gymnosperms are a group of plants with seeds but without flowers or fruits. The seeds are produced on the surface of sporophylls or scales or leaves. The seed-bearing sporophylls of the sporophyte are arranged in seed cones that develop at the same time as pollen cones. The pollen cones produce pollen grains. The seeds are exposed to the air and are directly fertilized by pollination.  The first seed plants that look-alike the appearance of ferns were primitively classified as ferns. They were reclassified as gymnosperms after the discovery of fossils with obvious seeds on the leaves. To this date, there are four phyla of living gymnosperms are recognized which are Phylum Pinophyta (Conifers), Phylum Ginkgophyta (Ginkgo), Phylum Cycadophyta (Cycads), and Phylum Gnetophyta (Gnetophytes). Pines (Pinus) are the most numerous conifers. The needlelike leaves are arranged in two to five clusters to makes them enable to adapt to rough environments such as high winds and bitterly cold temperatures. They mainly can be found in the Northern Hemisphere and Southern Hemisphere forests. Resin canals which develop in the mesophyll, secrete resin that suppress fungi and certain insect pests. Pine xylem is soft and has no vessel members and fibers. The phloem has no companion cells but has albuminous cells that have the same functions. Pine roots are always connected with mycorrhizal fungi, which are necessary in germination of pine seeds. Pine do not grow well in sterilized soil until fungi are introduced.  Conifers reproduce by generating two kinds of spores which are male microspores and female megaspores. These spores develop on separate male and female sporophylls on separate male and female cones. Microspores are produced in papery pollen cones that develop in clusters toward the tips of lower branches. The microsporangia develop in pairs toward the base of the pollen cone scales and give rise to four-celled pollen grains that occur in huge numbers. Megaspores are formed in ovules at the bases of seed cone scales. Each pollen grain produces a pollen tube that digests its way down to the developing archegonia, and two of the original four cells in the pollen grain migrate into the tube as it grows. The generative cell divides and produces a sterile cell and a spermatogenous cell that itself divides, producing two sperms. After pollination, one sperm unites with the egg, forming a zygote. The zygote develops into an embryo of a seed that has a membranous wing formed from a layer of the cone scale. Some conifers produce seeds enclosed in fleshy or berry-like coverings. Their evolutionary origin is not clear. There are many uses of pines. The seeds and inner bark of pines are edible, and a tea has been made from the leaves. Eastern wide pine stems were used as masts for sailing vessels and for crates, furniture, flooring, paneling, and matchsticks. Western wide pine is the source of most such lumber today. Resin from pines consist of turpentein and rosin. Turpentein is used as a solvent, and rosin is used by musicians and baseball players. Dammar from kauri pines is used in colorless varnishes. Amber is fossilized resin. Resin is also used in floor waxes, printer’s ink, paper coatings, perfumes and the manufacture of menthol. White spruce is the chief source of newsprint. It was also used for basketry and canoe lashing by Native Americans, with molasses or honey for treating scurvy, and in brewing a type of beer. Spruce resin was used for a type of chewing gum. The wood is used as soundboards for musical instruments and in the construction of aircraft. Larch and juniper woods are used for fence posts. Firs are used in the construction, paper, ornament and Christmas-tree industries. Douglas fir is probably the most desired timber tree in the world today. Coastal redwoods are also prized for their wood, which is resistant to fungi and insects. Bald cypress wood, used in the past for coffins and shingles, is also resistant to decay. A dye and tannis are obtained from the eastern hemlock. Native Americans used parts of hemlocks for poultices and for foods. Eastern white cedar’s wood was used for canoes, and that of the Atlantic cedar was used for construction of pipes for pipe organs. Yew wood is used for making bows, and an extract from yew bark has potential for the treatment of human ovarian cancer. Podocarps of New Zealand have edible seeds. Incense cedar wood is used for cedar chests, cigar boxes, pencils, and fence posts. Juniper berries are used to flavor gin and were used by Native Americans for food and beverages. Ginkgo has only one living species (Ginkgo biloba) with all others being extinct. The name which is derived from Chinese words meaning “silver apricot”. It is found in fossils 270 million years back and it is called as the living fossils. It is widely spread in the Northern Hemisphere. It has small, fan-shaped leaves with equally forking veins. The cultivation of Ginkgo is very popular in the US and are popular street trees in some areas. The life cycle of Ginkgo also similar to that of pines. The seeds are enclosed in a fleshly covering that has a rank odor when mature. Ginkgo seeds are edible and is used in traditional Chineese food, and Ginkgo plant extracts are used to improve blood circulation. Its various properties include act as an antibacterial and chemical defense. The first use as a medicine is recorded in the late 15th century in China. Among western countries, its first registered medicinal use was in Germany in 1965. Despite use, controlled studies do not support the extract’s efficacy for most of the indicated conditions. Cycads similarly resemble palm trees with unbranched trunks and crowns of large, separated leaves. Typically the cycad strobillus is found in the center of the plant. Lifecycles of cycads are correspondent to those of connifers, but the sperms of cycads include sperms with many flagella. Arrowroot starch was once obtained from a cycad. Gnetophytes are the only gymnosperms with vessels in their xylum. Genus Ephedra makes half of the species, which have jointed stems and leaves reduced to scales. Gnetum species have broad leaves and occur in the tropics, primarily as vines. Welwitschia is found in southwest African deserts. Its stem is in the form of a shallow cup with straplike leaves that extend from the rim. Mormon tea is brewed from the leaves and stems of joint firs (Ephedra), which, in the past, were also a source of the drug ephederine and a venereal disease treatment. One Gnetum species is cultivated in Java for food.