BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

IX. HIGHER SPORE PLANTS

Division Rhyniophyta (Rhyniophytes)

Rhyniophytes are exclusively fossil Water/159.html">HIGHER SPORE PLANTS. They were the first land plants to appear on Earth during the Silurian period of the Paleozoic era and became extinct in the Carboniferous period. Therefore, naturally, only fossil remains of these plants have been preserved. Only sporophytes have been discovered; gametophytes remain unknown.

The vegetative body of the rhyniophyte sporophyte lacked leaves and roots, consisting of cylindrical dichotomously branched Organs called telomes. Their lower parts formed rhizoids as outgrowths, while their apices terminated in sporangia. The telomes of rhyniophytes were covered with an epidermis containing Stomata. Beneath the epidermis lay the cortex, with densely packed outer Cells.

The center of the telome contained a concentric vascular bundle (protostele). The xylem was formed by annular tracheids, surrounded by 4-5 rows of elongated phloem cells. The telomes lacked cambium and mechanical Tissues. Rhyniophytes inhabited shallows and marshes, where they formed continuous thickets.

The Division Rhyniophyta includes a single Class, Rhyniopsida, and two orders: Rhyniales and Psilophytales. The order Rhyniales includes the genera Rhynia, Cooksonia, Yarravia, Horneophyton, and Hicklingia. The order Psilophytales is represented by the genera Psilophyton and Trimerophyton.

The Significance of rhyniophytes lies in the fact that they fundamentally altered the evolutionary trajectory of the plant kingdom from thalloid forms adapted to aquatic life to cormose (leaf-stem) forms inhabiting the land.

Rhyniophytes gave rise to the phylogeny of lycophytes, horsetails, ferns, and possibly bryophytes.