Cryptogams: An Introduction
What are cryptogams and how do they differ from other plants?
Cryptogams are a diverse group of non-flowering plants that reproduce without seeds. The name "cryptogam" comes from the Greek words "kryptos" (hidden) and "gamos" (marriage), referring to their less obvious method of reproduction compared to flowering plants (angiosperms). Instead of seeds, cryptogams use spores, an ancient form of reproduction that predates flowers and seeds. This group includes ferns, mosses, liverworts, hornworts, algae, and fungi.
Bryophytes are the simplest and oldest land plants, comprising mosses, liverworts, and hornworts. A defining characteristic of bryophytes is that they are non-vascular, meaning they lack specialised tissues (xylem and phloem) for transporting water and nutrients throughout the plant. Consequently, they are typically small and require moist environments to absorb water directly through their tissues. Their reproduction is also dependent on water, as their sperm need to swim through a film of moisture to reach the egg for fertilisation.
Common bryophytes include mosses, which often form dense mats and are highly adaptable, found in diverse environments. For instance, forest star moss has distinctive star-shaped 'leaves', and bank fir moss resembles a mini-conifer forest. Cypress-leaved moss is also very common, with 'leaves' similar to a leylandii hedge, growing on bare soil and tree trunks. Liverworts are smaller, flatter plants often with a liver-shaped appearance, with crescent-cup being a common imported species that can cover large damp areas. Hornworts are similar but less common, named for their horn-like sporophyte structures.
Pteridophytes, which include ferns and horsetails, are vascular plants. This means they possess specialised tissues for water and nutrient transport, allowing them to grow larger and inhabit a wider range of environments than non-vascular bryophytes. While they have this advancement, they still reproduce via spores, similar to bryophytes, rather than seeds. They also exhibit a more complex life cycle involving alternating generations between a spore-producing plant (sporophyte) and a gamete-producing plant (gametophyte).
Ferns are among the most well-known pteridophytes, identifiable by their large, divided leaves called fronds that unfurl from coiled fiddleheads. Spores are typically found in clusters called sori on the underside of their fronds. Common species in areas like Sidmouth include the very common male-fern and its variant, the scaly male-fern, as well as less common lady fern, hard fern, and broad-buckler fern. Bracken is ubiquitous in more open habitats during summer. Polypody ferns, distinguished by pores on the back of their 'leaves', can grow on soil, walls, and trees. Hart’s-tongue, a spleenwort rather than a true fern, is another frequently encountered member of this family.
Horsetails are closely related to ferns and are also pteridophytes, meaning they are vascular plants that reproduce using spores. They are characterised by their hollow, jointed stems and produce spores in cone-like structures at their tips. They are often found in wet or marshy environments. The greater horsetail is a particularly vigorous and almost "indestructible" species, known to spread quickly, especially along streams.
Spores are the primary means of reproduction for cryptogams. Unlike seeds, which contain an embryo and nutrient reserves, spores are typically single-celled reproductive units that can develop into a new organism without sexual fusion. This ancient method of reproduction allows cryptogams to disperse and colonise new areas, particularly in moist environments, as many cryptogam life cycles require water for the sperm to reach the egg for fertilisation.
While the term "cryptogams" historically encompassed various non-flowering, non-seed-bearing organisms that reproduce via spores, it's important to note that not all groups traditionally classified as cryptogams are considered plants. The provided source specifically mentions that "Fungi and Lichen" are cryptogams but are "not plants," indicating they are covered in a separate segment. This highlights that while they share the "hidden reproduction" characteristic, their biological classification differs from true plants like ferns and bryophytes.