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The plant kingdom and its divisions (16-Jan-03)

The plant kingdom comprises green algae (Chlorophyta) and the Streptophytes

These two groups share the photosynthetic pigments chlorophyll a and b, storage of photosynthate as starch within chloroplasts that are enclosed by a double membrane, and have cell walls made of cellulose.

Tree of Life website

Green algal groups are unicellular or colonial, whereas the green plants are true multicellular organisms with well-differentiated vegetative and reproductive structures. Green algae also have more varied life cycles, including one similar to that seen in the Embryophyta.

Photo of Volvox courtesy of Ohio University algae home page.

Volvox - Ohio University Algae website

Streptophytes include unicellular and colonial green algae with specialized ultrastructural features that are shared with the Embryophyta (see Judd et al. 2002, Fig. 7.2).

Photo of Micrasterias courtesy of Ohio University algae home page.

Volvox - Ohio University Algae website

Embryophyta comprise the non-vascular Bryophytes as well as all the vascular plant groups outlined below (see Judd et al. 2002, Fig. 7.8). The embryophyta all share a common life cycle with alternation between a diploid, spore-producing phase and a haploid, gamete producing one.


Lycophytes comprise extinct and modern club mosses and their allies, including at least two genera in which heterospory occurs (correct the label on Judd et al. 2002, Fig. 7.8). Lycophytes have small leaves with a single vascular strand.

Euphyllophytes have large leaves with complex vasculature, and comprise the two groups described below.

Monilophytes comprise ferns and horsetails, lack a vascular cambium, and are homosporous.

Lignophytes comprise living and fossil plants that not only produce secondary xylem, but also are heterosporous and form seeds (specialized megasporangia within which the embryo sporophyte develops and is dispersed).

Living seed plants comprise two groups, the "Gymnosperms" and the Angiospermopsida (see Judd et al. 2002, Fig. 7.12).

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