Ferns and Horsetails

1. Ferns, division Pterophyta; Chapter
   1. Reproductive structures -
      1. Sorus - collection of sporangia on abaxial surface of leaf (frond) lobes
      2. Sproangia - produce spores - haploid, unicellular gametophyge producing reproductive structure; no seeds, but vascular tissue is present; therefore, ferns are included with the horsetails as vascular spore plants.
         See additional material below regarding horsetail reproduction (very similar to that of ferns).
   2. Vegetative structures - the sporophyte is the dominant phase; vegetative structures are mostly the rhizome - underground stem with lateral roots emerging from the rhizome; the lobed leaves and leaflets are similar to the pinnately compound leaves of angiosperms; leaves are called fronds - composed of a blade portion called a pinna and a petiol portion called a stipe on simple fronds; leaflets of compound fronds are called pinnules
2. Horsetails, division Sphenophyta; Chapter
   1. Only one herbaceous genus, Equisetum; one dominant sp. in Oklahoma, E. hyemale; 15 spp. total in entire division; summary of classification:
      division Sphenophyta
      family Equisetaceae
      genus Equisetum
      species, dominant in Oklahoma, E. hyemale
   2. The dominant phase is the mature, adult sporophyte (diploid, spore-producing phase); reproduces by spores, not seeds; is vasuclar; therefore, is a member of the general group called the vascular spore plants.
   3. Reproductive structures:
      1. Strobilus - apical collection of sporangia.
      2. Sporangia - produce haploid, unicellular spores.
      3. Spores released from the sporangia germinate and produce a haploid, multicellular gametophyte. The gametophyte is larger than the 3- to 7-celled gametophytes of angiosperms and is also bisexual, producing both male and female gametes; the gametophyte is also, functionally more specialized in that root-like structures called rhizoids are produced and aid in water and nutrient uptake; male and female gamete-producing cells are localized within structures called:
         1. Archegonia - produce eggs
         2. Anteridia - produce sperm
      4. Sperm are released from the anteridium and swim to the archegonium to fertilize the eggs; absolute need for water in contrast to angiosperms and gymnosperms which contain sperm in the pollen which is transmitted by mechanical means such as wind, gravity, or animals.
      5. Young embryo develops within the archegonium and emerges to give rise to the adult sporophyte.
   4. Vegetative anatomy - hollow, jointed stems with rib-like structures and grooves containing large amounts of silica in the epidermis; leaves are very small and arranged in whorls around the joined nodes of the stem.