Pinophytina (Conifers)
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Pinophyta (Gymnosperms): Pinophytina (Conifers). The
Pinophytina are monoecious or dioecious seed-bearing shrubs or more often trees with
solid, woody, stems and freely branched, often symmetrical crowns. The leaves are simple,
alternate, opposite or whorled, often scalelike, needlelike or awl-shaped, or rarely
broad. Microsporangia are borne in simple male cones or strobili consisting of few to
numerous microsporophylls, each with usually 2-several microsporangia on the lower or
abaxial surface. One to several ovules are borne naked, usually on the surface of
ovuliferous scales that may represent highly modified shoots. Ovuliferous scales and their
associated bracts are usually spirally disposed on a central axis to form a compact,
compound megasporangiate strobilis or cone. One of four haploid megaspores derived from
meiosis of a megasporocyte in each ovule potentially yields a highly multicellular but
dependent female gametophyte bearing 1 or more archegonia, each containing an egg cell.
Pollen produced in the microsporangia is usually dispersed to the vicinity of the ovule by
wind. A pollen tube formed by the male gametophyte then delivers the nonmotile male
gametes through the micropyle and to the immediate vicinity of the egg whereupon
fertilization may occur. The developing embryo derives its nutrients from the female
gametophyte. Seeds are often winged.
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Pinophyta (Gymnosperms): Pinophytina (Conifers). The
Pinophytina are monoecious or dioecious seed-bearing shrubs or more often trees with
solid, woody, stems and freely branched, often symmetrical crowns. The leaves are simple,
alternate, opposite or whorled, often scalelike, needlelike or awl-shaped, or rarely
broad. Microsporangia are borne in simple male cones or strobili consisting of few to
numerous microsporophylls, each with usually 2-several microsporangia on the lower or
abaxial surface. One to several ovules are borne naked, usually on the surface of
ovuliferous scales that may represent highly modified shoots. Ovuliferous scales and their
associated bracts are usually spirally disposed on a central axis to form a compact,
compound megasporangiate strobilis or cone. One of four haploid megaspores derived from
meiosis of a megasporocyte in each ovule potentially yields a highly multicellular but
dependent female gametophyte bearing 1 or more archegonia, each containing an egg cell.
Pollen produced in the microsporangia is usually dispersed to the vicinity of the ovule by
wind. A pollen tube formed by the male gametophyte then delivers the nonmotile male
gametes through the micropyle and to the immediate vicinity of the egg whereupon
fertilization may occur. The developing embryo derives its nutrients from the female
gametophyte. Seeds are often winged.