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SEED PLANTS

      "Seeds" are another adaptation in which plant embryos are surrounded by a desiccation resistant coat to protect them from water loss.  There are two modern groups of seed plants: gymnosperms and angiosperms.  Gymnosperms are known from the end of the Paleozoic, the Permian.  Angiosperms (flowering plants) were the last group of plants to evolve and are the most successful group of plants alive on earth today.

 

GYMNOSPERMS

Gymnosperms (pines, cedars, hemlocks, spruces, junipers, etc.) and angiosperms (flowering plants) are the only plants alive which produce seeds.  More primitive plants produce spores in which the embryo possesses few resources.  In seeds, the embryo is surrounded by nutrients and tough seed coats.  Seed plants also developed more efficient ways to transport water through the trunk and sperm which were contained in pollen grains and not dependent on water for fertilization.

PINE CEDAR
Typically, the male cones (such as those or a white pine below) are smaller and simpler than the female cones.  Pollen from the male cones is transported by the wind to the female cones.  The growth of the pollen grains, pollination, and fertilization may require a year and the embryonic development which precedes the release of the seed may require another year.
MALE CONES
 

 

Today, conifers are successful in cold environments.  Their needlelike leaves have less surface area protecting them from water loss in areas of little precipitation and extreme cold (water is pretty hard to come by when the ground is frozen).  Conifers also include one of the tallest plants, the sequoia, which can reach 4,000 years of age, 340 ft. tall and 25 feet wide and bristlecone pines have reached 4600 years of age.

PINE HEMLOCK