Word of the Week: Ramentum

ramentum [ ra-men-tum, ruhmen-tuhm ] noun, plural ramenta: any one of the thin, chaffy, brownish, often fringed or laciniate scales borne upon the leaves or young shoots of certain ferns, and that consist of a single layer of cells

Ramenta on the fiddleheads of Dryopteris marginalis (marginal wood fern) in April. Photo © Elaine Mills

This word, related largely to ferns, usually appears in the plural, ramenta, and often with the modifier “chaffy,” as above. Chaff is the covering that is winnowed away from wheat after harvesting the grain, leading to the proverbial “separating the wheat from the chaff” – distinguishing between what is valuable and what is worthless.

However, we cannot assume the ramenta covering emerging fern shoots are useless. They appear to serve a protective role and are common in Dryopteris spp. where they envelop the growing point of the rhizome.  In Dryopteris marginalis (marginal wood fern), pale tawny ramenta occur in dense tufts. As the fiddleheads rise and the fronds unfurl and mature, the ramenta mostly dry up and fall away. In Dryopteris dilatata (broad buckler-fern), ramenta occur “in association with sporangia [spore-producing receptacles] forming a bud-like structure.” (Lang 1898)

The word ramentaceous, meaning covered in scales, is also used to describe the flower stem, footstalks, and undersurface of the leaves of Begonia ramentacea whose epithet also has this meaning.

References

Bayton R. 2020. The Gardener’s Botanical, An Encyclopedia of Latin Plant Names, Princeton University Press, Princeton, NJ.

Bower F O. 2010. The Ferns (Filicales): Volume 1, Analytical Examination of the Criteria of Comparison: Treated Comparatively with a View to Their Natural Classification. United Kingdom: Cambridge University Press. ISBN: 9781108013161, 1108013163.

Lang WH. 1898. On Apogamy and the Development of Sporangia Upon Fern Prothalli. Dulau and Company. p. 198. [digitized 2008 Feb 26].

Paxton J. 1844. Paxton’s Magazine of Botany, and Register of Flowering Plants 11:273. [scanned 2015 Aug 14].

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