The ancient quillworts are living fossils that have barely changed in 200 million years.

Gardening · Published 3 October 2026 Swipe more like this →

In short: Quillworts are mysterious, grass-like plants that have survived since the Jurassic epoch. Despite their simple appearance, these aquatic survivors use a complex form of carbon fixation usually reserved for desert plants and hide their reproductive cycles inside their own spores, making them a unique evolutionary puzzle for modern botanists.

Quillworts, or the genus Isoetes, are a group of about 200 to 250 species of lycopods that have remained remarkably consistent in form since the Jurassic. While the exact timing of their origin remains a subject of intense academic debate—with some molecular estimates suggesting a Cenozoic emergence and others pointing to the Mesozoic or Paleozoic—their morphology has stayed virtually unchanged for millions of years. The earliest fossil assigned to the genus, Isoetes beestonii, dates back to the late Permian, approximately 252 million years ago.

These plants are masters of adaptation, particularly in how they manage carbon. While most plants use crassulacean acid metabolism (CAM) to survive arid environments, quillworts use it to avoid competing for carbon dioxide in crowded aquatic habitats. Some species even absorb CO2 through their hollow roots from sediment rather than through their leaves. Their genome, first sequenced in I. taiwanensis, reveals that their CAM pathway is likely a result of convergent evolution, functioning differently than the CAM found in terrestrial angiosperms.

Reproduction in quillworts is equally specialized. As heterosporous plants, they produce both large megaspores and small microspores. Unlike ferns, which release their gametophytes into the environment, quillwort gametophytes develop entirely within the protection of the spore. To ensure survival, the sporophyte provisions these spores with starches, a strategy somewhat analogous to the energy investment seen in seed-bearing plants. Some species even practice synaptospory, where microspores are trapped in pockets on the megaspore coat, increasing the likelihood of successful fertilization upon dispersal.

Identifying these plants is notoriously difficult, as their vegetative traits vary wildly based on their environment. Botanists rely heavily on microscopic examination of spore ornamentation and the structure of the velum, a thin covering over the sporangia. Because of this complexity and the prevalence of hybridization, the phylogeny of the genus remains a point of contention, with many species currently listed as endangered due to habitat loss and pollution.

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