Introduction to the Vascular Plants

The Vascular Plants share the following characteristics which make them more complex (and generally considered more advanced) than the Bryophytes, which lack many of these characteristics.

 Vascular Plant Characteristics
  • Vascular tissue
  • Sporophyte generation independent and assimilative
  • Gametophyte often dependent on the sporophyte
  • Cutin and/or suberin produced on aerial parts
  • Body plan along an axis (the stem)
  • Generally large surface area/volume ratio (Allows land survival with less surface H2O)
  • Xylem promotes (allows) increase in size

    Classification of the Vascular Plants
     There are several Divisions (as mentioned), Subdivisions and Classes
    Many important for fossil roles
    Discuss in general direction of advancement and complexity
    Features used in classifying the Vascular Plants
     Vascularization -- Microphylls vs Megaphylls for leaves
    Dispersal Sperm transport The type of sporangia is also a feature used in classification. Some plants produce one type of sporangium, and are called homosporous. Other plants produce two different sporangia, megasporangia and microsporangia and are heterosporous.

    A plant which is homosporous can produce either one kind of spore, which grows into a gametophyte which contains both male and female reproductive structures (the antheridium and archegonium, respectively) or a homosporous plant can produce two types of spores (but still within one sporangium). When two types of spores are produced, one type of spore will grow into male gametophytes, producing only antheridia, and the second type of spore will grow into female gametophytes, producing only archegonia.

    Heterosporous plants always have separate sporangia, and the microsporangia produce only microspores which grow into male gametophytes, producing only antheridia. The megasporangia produce megaspores which grow into female gametophytes, producing only archegonia. The megasporangia and microsporangia may be found on the same sporophyte individual, or on separate individuals. The Vascular Plants are divided into two groups.
    Lower Vascular Plants which disperse via spores
     Psilotophyta
    Lycophyta

    Sphenophyta
    Pterophyta


    Higher Vascular Plants which disperse via seeds
     The Fossil Seed Ferns
    The Gymnosperms
    The Angiosperms