are now extinct, but their smaller relatives still remain. Seedless vascular plants include the
club mosses, the ferns, the horsetails, and the whisk ferns.
Club mosses,in the phylum Lycophyta, are so named because they can look similar to
mosses(Figure10.11). Clubmosses arenottruemosses, though, becausethey havevascular
tissue. The “club” part of the name comes from club-like clusters of sporangia in some types
of club mosses. The resurrection plant is also a club moss. It shrivels and turns brown when
it dries out, but then quickly recovers and turns green when watered again.
Figure 10.11: Club mosses can superficially resemble mosses, but they have vascular tissue.
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Ferns,in the phylum Pterophyta, are the most common seedless vascular plants (Figure
10.12). They typically have large divided leaves called fronds. In most ferns, fronds develop
from a curled-up formation called a fiddlehead (Figure10.13). The fiddlehead resembles
the curled decoration on the end of a stringed instrument, such as a fiddle. Leaves unroll as
the fiddleheads grow and expand. Ferns grow in a variety of habitats, ranging in size from
tiny aquatic species to giant tropical plants.
Thehorsetails,the phylum Sphenophyta, have hollow, ribbed stems and are often found
in marshes (Figure10.14). Whorls of tiny leaves around the stem make the plant look like
a horse’s tail, but these soon fall off and leave the photosynthetic hollow stem. The stems
are rigid and rough to the touch as they are coated with abrasive silicates. Because of their
scratchy texture, these plants were once used as scouring pads for cleaning dishes.
Thewhisk ferns,the phylum Psilophyta, have green branching stems with no leaves, so
they resemble a whisk broom (Figure10.15). Another striking feature of the whisk ferns is
their spherical yellow sporangia.