Seed not completely enclosed.
Gymno = naked
sperms = seeds
Seed Plant Synapomorphies
3. Vascular cambium and cork cambium
Formation of two types of spores within two types of sporangia.
Large, few in number.
Develop via meiosis within megasporangium.
Develop into female gametophyte.
Smaller, more numerous.
Develop via meiosis within microsporangium.
Develop into male gametophyte.
Embryo, nutritive tissue, and seed coat.
Complete development of immature male (or female) gametophyte within original spore wall.
Formation of pollen tube.
Wood - adds structural support to a plant, enabling it to grow tall and produce lots of lateral branches.
Provide protection to the bark of trees and shrubs.
Similar vessels in xylem to angiosperms.
No antheridia or archegonia.
Probably where the ancestor of flowering plants came from.
About 30 species.
Trees and climbing vines with large, leathery leaves that resemble those of dicots.
Inhabit moist tropics of South America, west Africa, and southeast Asia.
About 35 species.
Profusely branched shrubs that inhabit arid or desert regions.
Six species in the southwest United States.
Inhabit southeast Asia.
Most of the plant is buried in the soil.
Above-ground part is a woody, concave disc that produces only two strap-like leaves.
Cones produced on the margins of the disc.
Unique fertilization - tubes from the eggs grow up toward, and unite with, the pollen tubes. Fertilization occurs in the united tubes.
Short stems and big leaves.
Zamia is the only native U.S. species - it has a short vertical stem and a crown of spirally arranged, leathery, dark green, pinnately compounded leaves.
Monotypic phylum - only one living species.
Ginkgo biloba appeared at least 280 million years ago during the Permian period. It is commonly cultivated due to air pollution resistance. It might still grow wild in China.
The leaves are fan-shaped and have dichotomous venation.
About 550 species in 50 genera.
Appeared at least 290 million years ago during the late Carboniferous period.
Each individual produces male and female parts.
Divides to make two sperm cells.
Function is unknown.
Includes a sterile bract, ovuliferous scale, micropyle, integument, and megasporocyte.