Mojave National Preserve - Ferns

The delicate maidenhair fern ( Adiantum capillus-veneris ) is found at Cornfield Spring. (C. Munill) Ferns are the second most diverse group of living land plants (after flowering plants) with approximately 12,000 species described worldwide. Fossil ferns have been discovered from the Devonian period (410 - 360 million years ago). These early ferns evolved from the earliest vascular plants. The Carboniferous period (360 - 285 million years ago) is often called the Age of Ferns because it was during this period that ferns achieved their greatest diversity and dominance over the plant world.

Ferns are vascular plants but they reproduce via spores like the non-vascular plants (for example, mosses). Also like non-vascular plants, ferns have two distinct life phases, the gametophyte and the sporophyte, and a complicated reproductive system. In ferns, the gametophyte phase consists of tiny independent plants less than " across. The gametophytes grow male organs (antheridia) which produce spermatozoids, and female organs (archegonia) which produce eggs. The spermatazoids swim to the eggs through water droplets and fertilize them. The fertilized eggs grow to produce sporophytes, the large, vegetative plants that we usually think of as ferns.

Although ferns are typically thought of as inhabiting shaded moist habitats some ferns live in dry areas such as deserts. Sixteen species representing three families have been documented in Mojave National Preserve. Some of these ferns are adapted to the generally dry conditions and irregular rainfall and are termed xerophytic ferns. Examples of these ferns include species of the genera Pellaea and Notholaena , which have a waxy coating on the frond blades, and Cheilanthes and Astrolepis , which have scale-covered leaves. Some species of Pellaea have fronds that dry out during long dry periods. Still others, such as the delicate maidenhair fern ( Adiantum capillus-veneris ), grow only in areas where there is water available, such as at seeps and springs.