Among the first plants to live on land, nonvascular plants are simple, low-growing organisms that rely on moisture to survive. Nonvascular seedless plants, also known as bryophytes, lack vascular tissue and lignin—the rigid material that allows other plants to grow tall and remain upright. Because of this, they do not have true roots, stems, or leaves. Instead, they remain small and close to the ground, thriving in damp environments where they can absorb water and nutrients directly through their surfaces.

Bryophytes include mosses, hornworts, and liverworts, and they have a life cycle that alternates between two stages. In the gametophyte stage, the plant produces male and female sex cells, or gametes. When these gametes unite, they form a zygote. In the next stage, the zygote develops into a sporophyte, which grows attached to and depends on the gametophyte. The sporophyte then produces spores, continuing the cycle.

Different types of bryophytes have unique features. Hornworts are named for their long, horn-like sporophytes and are commonly found in moist, humid environments. Liverworts often grow along streams or in damp soil and are named for the liver-shaped appearance of their gametophytes.

Vascular seedless plants, also known as pteridophytes, are more advanced than nonvascular plants because they have lignin-hardened tissues that provide support. Unlike bryophytes, they have true roots, stems, and leaves, along with specialized vascular tissue that transports water, minerals, and sugars throughout the plant. However, they do not produce seeds; instead, they reproduce using spores.

Like other plants, vascular seedless plants have a life cycle that alternates between two stages. In the sporophyte stage, the plant produces spores. These spores grow into small gametophytes, which produce male and female sex cells, or gametes. When fertilization occurs, a zygote forms and develops into a new sporophyte plant, continuing the cycle.

This group includes ferns, clubmosses, and horsetails, each with distinct characteristics. Ferns are the most common, with over 12,000 species, and have large, divided leaves called fronds. Clubmosses, despite their name, are vascular plants and often grow along forest floors. Horsetails typically grow in moist or sandy areas and have stems that contain silica, giving them a rough texture that was once used for scrubbing pots and pans.

Review:

1. What characteristics do bryophytes share?
2. What characteristics do pteridophytes share?
3. Where are clubmosses typically found?