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Vascular Plants - a quick review - page 7 / 12

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Phylum Lycopodiophyta

Isoetaceae - quillworts

Heterosporous plants with sporangia borne at the base of sporophylls which are similar to vegetative leaves. Megasporangia + microsporangia

Phylum Polypodiophyta

Equisetaceae - horsetails, scouring rushes

Leaves in whorls; leaves one veined, verticillate, united to form a sheath around the stem; these leaves are probably reduced megaphylls: Megaphylls are larger than microphylls have a blade that has a complex system of veins.

megaphyll

sheath

branch

Megaphyll theory is supported by placement of Equisetum among primitive ferns using DNA.

Phylum Polypodiophyta - ferns & horsetails

Equisetaceae - horsetails, scouring rushes

[previously placed in own phylum - Equisetophyta]

1 genus, Equisetum, 15 species with a cosmopolitan distribution except for Australia or New Zealand [9 species in Wisconsin]

Plants are primarily colonizers of unforested areas, lake margins and wetlands

Shoots monomorphic or dimorphic (see right).

Often highly branched (horsetails) appearing like leaves. Others not branched (scouring rushes).

Internodes with conspicuous vertical ridges; jointed stems; stems hollow (both important taxonomic features for keying species)

Phylum Polypodiophyta

Equisetaceae - horsetails, scouring rushes

Sporangia clustered terminally in cones composed of polygonal, umbrella-like structures with sporangia beneath.

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