Fossil ferns

Fossil ferns

Fossils of ferns are numerous from the mid-Devonian period onwards. They were important in the coal measures of the Carboniferous period. There were many tree ferns and non-woody species with various branching patterns. The fossils provide evidence, mainly from leaf form, that ferns probably evolved from the Trimerophytopsida . Sporangia of all the early ferns were eusporangiate. True leptosporangia, as seen in most modern ferns, probably did not appear until the Cretaceous period ( Table 1). Living leptosporangiate ferns evolved in parallel with the flowering plants in recent epochs.

    Several fossil ferns from the mid-Carboniferous period and later were heterosporous. They are not directly related to the living heterosporous water ferns and it is clear that heterospory has evolved several times within the ferns.

Ferns and man

Considering their abundance, our uses of ferns have been limited, although bracken was extensively used for animal bedding and as kindling in Europe. The young developing leaves of bracken and some other ferns have been harvested as food for centuries, sometimes much sought after as a delicacy and still eaten, particularly in the Far East. Unfortunately some are carcinogenic and there is a relationship between regular eating of fern shoots and throat or esophageal cancer.

   The main current use for ferns is as ornamentals. Their feathery leaves have long been admired and some rare species have been much sought after, as a result becoming rarer. Leaves are used in flower arrangements as background and orchids and other epiphytes are often grown on pieces of tree fern trunk or in a fibrous soil made from crushed fern leaves.