Linda Lee
No gaudy flowers for this humble little earthling. No flowers at all – not even seeds. Here’s a plant that reproduces solely by spores and shares affinities with the familiar ferns. Some people might look at this plant and think it’s a moss of some sort – it’s not. It is richly supplied with vascular tissue – xylem and phloem, of course – for conducting water and solutes. The true mosses lack such conducting tissues.
This is one of about 90 similar species, all belonging to the same genus and mostly distributed in North America. They are all diminutive plants, just a few inches tall, but often occurring in massive growths, forming patches or extensive mats. And they are frequently found in arid habitats, either on open rock or on bare sand.
Growing in inhospitable places can be a struggle, so plants growing in such places must adapt to extremes in solar radiation and surface temperatures, as well as extremely dry environments. The plants produce wiry stems with plenty of short, wispy leaves, each with a tiny, curved bristle at the tip. These leaves are very simple structures and, anatomically, aren’t exactly the same kind of “true” leaves found on a maple tree or a rosebush.
Although they have little or no human economic value, these various species are quite important in their natural settings. Those that thrive on bare rock are effective in trapping sand and sediment, allowing colonization by other, often larger, plants and providing habitat for a variety of small critters.
The spores are produced in special pouches at the base of a leaf. There are two different kinds. Megaspores are relatively large, and they end up producing a tiny structure bearing egg cells. The microspores are much smaller, and they eventually supply tiny sperm cells that affect fertilization. The plants represented by the leafy mats are ultimately the result of this kind of fertilization, which, as you might expect, can only take place when there is a film of water covering the plants, either from rain or dew.
The plant pictured here represents one of the various species which grows only on open rock, known to occur at high elevations in the Carolinas and Georgia. You’ll also see some broken glass on the rock surface, which suggests human visitation. Sure enough, open flat-rock habitats and domes have always been attractive to people for a variety of reasons for thousands of years.
Recreational possibilities abound in such places, but, unfortunately, most flat-rock sites in the Southeast are currently threatened by destructive activities of their human visitors, including bonfires, spray-painting, smashing bottles and joyriding. Sadly, many of the best sites we know of have been seriously harmed in this way, with the resultant loss of characteristic plant life, including a number of rare species. Fortunately, there are several excellent examples of protected flat-rock ecosystems available for responsible visitation and hiking.
Answer: “Spike-moss,” Bryodesma tortipilum
John Nelson is the retired curator of the Herbarium at the University of South Carolina. As a public service, the Herbarium offers free plant identifications. For more information, visit herbarium.org or email johnbnelson@sc.rr.com.