Club Mosses

Lycopodium is an example of club mosses. These plants are often seen in the woods and may be mistaken for pine seedlings. In fact, they go by the vernacular name "ground pines." The sporophytes produce upright stems, which bear minute leaves, called microsporophylls, each having a single, central vein without branches. Stomates can be found on both surfaces of the leaves. The leaves arise without forming leaf gaps (an advanced characteristic found

Spore Formation Sporangia

Spores Released o

Indusium

Sporangium

Enlarged View of Leaf Underside Showing Sori

Leaf Surface

Sporangium With Spores Mosses

Collared Cell

Lip Cell

Sporangium

Enlarged View of Leaf Underside Showing Sori

Spores Released

Indusium

Collared Cell

Leaf Surface

Lip Cell

Young Sporophyte Notch

Archegonia

Gametophyte

Antheridia

Germinating Spore

Sporophyte Growing, Still Attached to Gametophyte

Sperm Released

Immature Archegonium with Neck Cells Still Intact

Sperm Magnified

Gametophyte

Foot Embeded in Ventor of Archegonium

\ Mature Archegonium with Egg

After Fertilization Embryo Sporophyte Grows in Ventor

Figure 25-2 The gametophyte generation in the life cycle of fern, (a) A spore germinates to produce the first few cells of the gametophyte. (b) The heart-shaped, mature gametophyte. (c) Antheridia among the rhizoids. (d) Archegonia near the notch of the upper portion of the gametophyte. (e) An antheridium opens to release sperm, (f) A much magnified sperm cell, showing many cilia, (g) An immature archegonium with the neck canal cells still intact, (h) A mature archegonium with an egg. (i) The embryo sporophyte growing in the venter of the archegonium. (j) The young sporophyte sends a root downward and a shoot upward with the primordium its first leaf, (k) The sporophyte continues, still attached to the gametophyte.

in higher plants and defined as an interruption of the vascular tissue immediately above the leaf trace).

The vascular tissue is similar to that in higher plants. The xylem and phloem alternate, producing a pattern similar to that found in the roots of higher plants. The stems and roots grow up from horizontal rhizomes (stems).

# Notes * Such roots are called adventitious. Sporangia are borne in clusters, forming club-shaped strobili (strobulus). Spore mother cells undergo meiotic divisions, and the resulting meiospores grow into minute gametophytes.

The gametophytes bear both antheridia and archegonia. Biflagellated sperm cells swim to the venter of the archegonium to fertilize the egg cell, which is then the first cell of the new sporophyte generation.

Some species of Lycopodium form small masses of tissue called bulbils, which may drop off to form new sporophytes. This is a vegetative means of reproduction; no sex is involved.

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