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CONIFERS IMAGES
1. The coastal redwood trees, the world's tallest conifer, Sequoia sempervirens.
2. A cedar tree (Cedrus) along the Monterey Peninsula in Northern California; note that all members of the Coniferophyta are woody trees or shrubs, which means that they all undergo secondary growth.
3. Transverse section of a needle of Pinus nigra, a species with 2 needles per fascicle.
4. Close up of a sunken stomate on a pine leaf.
5. Transverse section through an entire fascicle in a Pinus species, with 3 needles per fascicle.
6. Transverse section through a young stem of Pinus; the eustele has been modified by the production of secondary xylem and phloem.
7. Transverse section through a portion of pine wood, showing part of three growth rings; note the resin canals that are scattered through the wood.
8. Section through an ovuliferous scale of pine, with an ovule at the megaspore mother cell stage. The enlarged megaspore mother cell, which is surrounded by the nucellus or megasporangial tissue, will undergo meiosis to produce the functional megaspore of the ovule. It is at this stage that pollination occurs. After pollen enters the micropyle, the ovuliferous scales grow together to close up the cone.
9. Longitudinal section of an ovuliferous scale of pine, after development of the female gametophyte and archegonia. Identify the archegonium, female gametophyte, nucellus and scale proper. This is the stage of the cone seen in slide 10.
10. A developing seed cone of Pinus, after one years growth. At this stage the female gametophyte has developed and the archegonia and egg cells are present. This size cone is called a second year cone.
11. A magnified view of the egg cell in an archegonium of the female gametophyte of pine.
12. Pollen cones at the stage of pollen release.
13. A preparation of pine pollen, showing the wing-like bladders that have been produced from the spore wall.
14. Fleshy cones of the Juniper, often called juniper "berries." These are actually seed cones, not berries, which are a type of fruit.
15. The ovule producing structure in Taxus, or yew. This is the one group of conifers that does not produce seed cones, but rather produces the ovule on a short branch. The ovule is surrounded by a red fleshy structure called an aril. In this genus the seeds are dispersed by birds.
16. Compound pollen cones of the gnetophyte, Ephedra. In this group of gymnosperms the microsporangia are clustered at the apex of a group of fused microsporophylls on a branch that is inserted in the axils of large bracts.
17. A seed-bearing plant of Ephedra, with compound seed cones. This taxon has long internodes and only small, scale-like leaves. The seed cones are compound, meaning they bear bracts on an axis, with ovule-bearing branches in their axils.
18. A higher magnification of a seed cone of Ephedra.
19. The exotic gnetophyte known as Welwitschia known only from the Namib Desert of southwest Africa.
