The plant kingdom includes one celled organisms (diatoms) as well as
complex organisms like angiosperms. Some plants and trees (tracheophytes)
have vascular tissue or well-developed conducting tissue through which
water and solutes are transported to various parts of the plant. Other
plants are non-vascular (bryophytes) and do not possess internal
transport systems. Most non-vascular plants live in water or in wet
environments that facilitate the direct diffusion of water and
nutrients. Vascular plants, however, live on land and possess special
features adapted to this environment such as roots, stems and leaves. As
in most classification systems, not all botanists agree on the same
classification system or the same categories. In this program we are
using the following simplified classification scheme:
Brown-green algae refers mainly to one-celled plants called
diatoms. These form major component of the oceans and are important
because they are at the bottom of the food chain and are responsible
for some oil formation.
Brown-red algae refers to the large plants of the sea, including
kelp and seaweed. Plants in the marine environment do not need the
elaborate vascular conducting system of land plants for transporting
nutrients because the marine environment has all these nutrients
available. Bryophyta, which include mosses and liverworts, are mainly
inconspicuous plants growing in moist habitats. They are not fully
adapted to life on land because they need water to reproduce.
Bryophytes do not get very large.
Sphenophyta or horsetails are easily recognized by their
jointed stems and rough, ribbed texture. Early settlers used
horsetails to help clean pots and pans because of their rough texture.
You find these plants in wet environments.
Ferns (filicopsids) are familiar vascular land plants that
reproduce by using spores rather than seeds. Ferns prefer wet, moist
climates.
Gymnosperms (which includes Ginkgoes) or conifers (pine-like
trees) are mainly cone-bearing plants. There are only about 550
species of living conifers. They dominate the forest of the Northern
Hemisphere, but are known in the tropics and Southern Hemisphere. The
leaves of most conifers are needle-shaped and are all simple or have
scales.
Angiosperms (flowering plants) produce a seed cover for
reproduction and are the most common small plants and trees. They are
divided into monocots (grasses) and dicots (larger flowering plants).
