Lower (non-seed) vascular plants

The "lower vascular plants" is a group composed mainly of ferns, but also includes the club mosses (Lycopodium), the horsetails (Equisetum), and the whisks ferns (Psilotum) as well as a few others.  

figure 12

Figure 12 Some typical non-seed vascular plants  

A. Fern life cycle
Note large sporophyte or what we recognize as the typical fern. The small gametophyte produced by our local ferns for a short time in the spring is small and almost never observed by non-biologists.

B. Club moss with upright spore containing reproductive structures  The gametophyte is not present in this photograph.  

C. Horsetail with terminal spore containing bodies
Again only the sporophyte is pictured.   

This is a group of land plants that first appeared during the early Carboniferous period and quickly came to dominate the plant community of that time. Most of the fossil fuels we rely on today to fuel our world are derived from extensive fern forests from this period. A great fern radiation occurred in the late Cretaceous when most modern families appeared. Ferns still compose a sizable portion of the current plant community but extant species do not grow to the sizes achieved by their ancestors. The epidermal cells of ferns produce a waxy cuticle that helps prevent water loss. Stomata, small openings on the stems and leaves that allow plants to perform gas exchange with the atmosphere, are also present. Primary structures of ferns include roots, stems, vegetative  fronds, and reproductive fronds (structures with sporangia that produce spores). These plants produce no flowers, seeds, or fruits. They do have vascular tissue in the form of xylem to transport water and phloem to transport food to all parts of the plant. Vascular tissue includes cells with rigid cell walls providing structural support and strength. Increased strength and water movement allowed plants to begin colonizing the drier terrestrial environments and to increase their size well beyond the size of the non-vascular plants.  Lower (Non-seed) Vascular Plants show alteration of generations with the sporophyte as the dominant stage. The reduced gametophyte generation produces motile sperm that swim to fertilize stationary eggs which begins the sporophyte generation. 

In the following animation, you can observe a male gametophyte of the C fern releasing sperm.  The gametophyte is still attached to the striped spore.  Note the shape of fern sperm.

View video of C-fern sperm

Young sporophytes are initially dependant on the gametophyte for food and nutrients before they can fully support themselves. When sporophytes are self sufficient, the gametophyte slowly withers and dies. Most people never observe the tiny gametophyte generation since it is so small and short-lived.  View the following animation on fern development. Note that in both the non-vascular and lower vascular plants, structures that produce sperm are known as antheridia and the structures that produce eggs are known as archegonia

View animation of fern life cycle