A rare chance at seeing how some spikemosses launch the next generation into new heights. Written by Mo Inall, internship student during summer 2025 at the Molecular Palaeobotany and Evolution Group.Selaginella kraussiana, or Krauss’s spikemoss, is a small creeping plant belonging to a group known as the Lycophytes. They are studied in the Hetherington lab here in the institute due to their interesting evolutionary position - they branched off from true-leaved plants early on in the history of vascular land plants, and to this day retain several features of the very first vascular plants. It is one of two species I have been studying during my internship in the lab with postdocs Dr. Róisín Fattorini and Dr. David Hoey.Hetherington lab One particularly interesting feature of S. kraussiana are its strobili, tall sexual structures housing the spores by which it reproduces. The strobili have many microsporangia, and a single megasporangium at the base. These strobili have proved challenging to produce under laboratory conditions, but putting the plant under stress seems to have been a successful method. This may be because if conditions in the environment are hard, then the response of the plant is to increase genetic diversity by sexual reproduction, to have a better chance at surviving in its environment.Looking at these structures under the microscope I noticed something amazing – the microsporangia were splitting open and pinging out of the strobili, spraying spores many times the distance of a single plant. David and I captured the following video of this behaviour with the Keyence VHX-X1 digital microscope. Real-time footage of a strobilus of Selaginella kraussiana where one can see multiple microsporangia sacs dehiscing (opening) and being launched into the air by projectile action of the catapult-like movement of the bracts (sterile leafy structures that protect the sporangia during development). Interestingly, this phenomenon is poorly documented in lycophytes, although it is not a complete surprise, as they have historically not been well studied. Projectile spores are well described in a number of fern species, but in S. kraussiana there are very few mentions of this ability. Koller and Schekler (1986) describe a raised band of dead, water filled cells reinforced by lignin (a tough polymer that makes plants woody) running around the sporangia. As the sporangium dries, pockets of water vapour form in the band of lignified cells, driving it to split open or ‘dehisce’ into two halves. These act as valves, slowly pushing back the modified leaf housing our microsporangium, and pushing against the stem of the strobilus at the same time. This pressure actually breaks the stem, and resulting release of tension sends the entire microsporangium flying up to 20cm away. What a fascinating process for a plant to help disperse the next generation!A special thanks to Dr. Róisín Fattorini who co-supervised Mo's project in the Hetherington lab on a related project focused on Selaginella.Raw videoRaw videos have been uploaded to the University of Edinburgh datashare:Hoey, David J; Inall, Mo; Hetherington, Alexander J. (2026). Explosive spore dispersal of Selaginella kraussiana, [dataset]. University of Edinburgh. School of Biological Scienceshttps://doi.org/10.7488/ds/8069.Selected readingKoller, A. L., & Scheckler, S. E. (1986). Variations in Microsporangia and Microspore Dispersal in Selaginella. American Journal of Botany, 73(9), 1274–1288. https://doi.org/10.2307/2444062 This article was published on Wednesday 7 October 2026
