Macbridea – Birds-in-a-Nest

The Back Story

A delightful plant to encounter in Apalachicola’s Pine Flatwoods, the lovely and unmistakable Macbridea alba is sometimes called White Birds-in-a-Nest.  This wouldn’t be an everyday encounter, rather an infrequent event to celebrate.  The Gulf Coast Macbridea is a rare endemic, reported only from 4 counties (Bay, Gulf, Liberty, and Franklin) here in the Apalachicola region. It’s not simply rare geographically, considered Endangered, here in Florida, but rare taxonomically.  

The 1860 publication of Macbridea alba by Chapman

Few plants in our flora that have been known for over one and a half centuries can be listed without synonyms.  A. W. Chapman described Macbridea alba in the second edition (1860) of his Flora, and not a single taxonomist seems to have disagreed, in over 8 score years. That’s noteworthy, like a town that has only one Baptist church.

What’s so remarkable about Macbridea is that there seem to be only two species in the genus, our M. alba and the somewhat more widespread Atlantic Coast Macbridea caroliniana, which was discovered, earlier, and published twice before Chapman recognized the Apalachicola species.  The slightly more complex history involves Thomas Nuttall, who worked in Philadelphia and published his landmark Genera of North American Plants in 1818, who corresponded with the very well-connected Stephen Elliott of Charleston, SC.  On page 36 in Vol 2 of Genera, Nuttall included Elliott’s description of Macbridea pulchra, thus publishing the genus and species simultaneously.  Nuttall’s entry was succinct, including nothing about Elliott’s reasoning for the name choice.  

However, he gave us a bit of information that helps explain the name by which we call this plant today – Macbridea caroliniana.  Reading the Nuttall entry, he cites Thymbra caroliniana, Walter, p. 162 as synonymous to Elliott’s plant – clueing us into the fact that Walter had recognized the same plant earlier, in his 1788 Flora, tucking his find into the Mediterranean genus Thymbra.  The fallout, of course, is that Walter’s specific epithet takes priority, supplanting Elliott’s epithet pulchra – a term botanist use to tell us a plant is ‘beautiful’.  The name for this plant, then, becomes Macbridea caroliniana (Walter) S. F. Blake.  But that didn’t happen until 1915; Chapman, when publishing Macbridea alba in 1860, also cited the Carolina plant as Elliott’s Macbridea pulchra – 45 years before Blake’s clarifying article. But Stephen Blake, lauded for his expertise in historical taxonomic issues, had slogged through the muddle of Walter’s herbarium, held at the British Museum, which he describes as “occupying 117 pages in a large volume.” 

Blake accepted the genus Macbridea, but neither Nuttall, nor Chapman, nor Blake ever gave us the story behind this name. We have to read introductions in both volumes of Elliott’s important Sketch to learn more. James Macbride, a young doctor and flourishing botanist, worked in the small town of Vineland, not far from Charleston, where Elliott lived. He had become a significant botanical resource for Elliott, but the good die young.  Macbride succumbed to a plague of yellow fever in 1817 (at an age of 33), leaving Elliott to “advertise” Macbride’s contributions in vol 1 of A Sketch of the Botany of South Carolina and Georgia (1821)

“I have subjoined, occasionally, to the description of the plants, observations on their medical and economical uses.  For the medical observations I have been indebted to Dr. James Macbride, a gentleman who unitizing great sagacity and talent, to extensive and accurate botanical knowledge, has made the medical properties of our plants a subject of careful investigation.  His particular object has been to ascertain what plants really possess peculiar and valuable qualities; not merely to amass without discrimination, popular receipts.  The results of his researches, I can offer with confidence to public notice.”

and to dedicate the second volume, 1824, following a list of important contributers who had perished, Elliott returned to MacBride:

 “to the late Dr. James McBride a tribute is due not only for the services which he himself actually rendered, but for the contributions which he induced others to offer.  Devotedly attached to science, he had the talent to make it popular wherever his influence extended.  Profoundly skilled in his profession and high in the confidence of his fellow citizens, he fell a victim to the fatigues and exposure of an extensive practice,  In the midst of a brilliant career with prospects of increasing usefulness and extended reputation, he died at the early age of cc.  he left to many friends a mournful inheritance —- the task of lamenting one so highly gifted, so prematurely lost.  To HIS MEMORY THIS VOLUME IS INSCRIBED as a testimonial of long continued friendship and of unabated respect.  It is among the incidents which embitter life that those who have shared in common labour should so often be separated before the termination of their pursuits.  The individuals who took most interest in this sketch scarcely lived to see the commencement of its publication.  IT IS TO THE DEAD THE AUTHOR HAS TO CONSECRATE THE RESULT OF HIS LABOURS”

The story of James MacBride doesn’t end with A Sketch…  Meeting in Mobile, in 1996, foresters and researchers held the ‘First Long Leaf Pine Alliance Conference’.  A historical paper, presented at that meeting (by researchers out of Tall Pines), described past efforts to characterize the Long Leaf Pine ecosystem, the earliest being an unpublished list written by James MacBride (preserved in the Elliott manuscript files at Harvard University) describing 17 Long Leaf Pine forest floor associates.  The researchers collated MacBride’s list with other historical efforts, as well as contemporary studies.  MacBride, listed as an author, is on record as having made one of our earliest contributions to ecological studies of the Longleaf Pine system.

Macbridea alba with Verbesina chapmanii, a common associate

The Main Story

I don’t know when or where the common name Birds-in-a-Nest was first given to the two Macbridea species, but it’s just one charming aspect of this enchanting plant couple.  The herb you might be fortunate to encounter in the Apalachicola area is the white-flowered Gulf Coast species, while you’d have to visit coastal Georgia or South Carolina to see its equally rare, rich pink congener. 

Though our White Birds-in-a-Nest is readily recognized in flower, it stands out based on foliage alone.  This is a mint, so one expects squarish stems and opposite leaves.  Among its many distinctive features, the plant is slightly chartreuse and somewhat succulent, the leaves being oblanceolate. 

It’s described as a rhizomatous perennial, but every plant I’ve seen presents itself as an annual – there’s no strongly-rooted base from which stems emerge.  The foliage is absolutely distinctive, leaf pairs distributed evenly but distantly along the stem.  Leaves are oblanceolate and broadly attached, the lower ones over 7 cm long, reducing in length from base to the flowering apex.  You might read descriptions that speak of occasional trichomes or margins being remotely toothed, but in my mind, the overwhelming appearance of a fresh leaf is smooth thickness, with rounded, molded margins, which contractors would describe as “bullnose.”  There is often a remote, soft prickliness to the margins, but not diagnostic. Looking at herbarium specimens, the shallow toothing (which marks the Carolina species) seems evident, but in live plants that isn’t a prominent character.  Though unrelated, the leaves resemble those of Polygala lutea…, on steroids.

An upper leaf on a Macbridea alba stem

The most striking character is the surface pitting, described as glandular punctuation, present on both surfaces of the thickened leaves and floral bracts.  Picture the texture of an orange peel. and you’re at the best description of surface texture I can conjure.  It would be possible to identify the plant from a single leaf.  I haven’t seen anatomical studies of the leaves, but would truly like to learn more about the nature of these pits; in touching leaves I do not sense resin, and though Macbridea is in the mint family, I perceive no essential oil character to the plant.

Epidermal pitting on leaves and bracts

The flowering structure is diagnostic, a clustered head of buds subtended by large, round, green bracts of the same character as the leaves.  Each bract subtends and cups around a developing flower, which begins as a white knob-like (or egg-in-a-nest-like) bud. 

Flowers are respectably large, the few I’ve measured would fit in  3×3×3 frames – that’s 3 cm across the front, 3 cm in tube length, and just under 3 cm, looking straight at the flower, from top to bottom.  From a distance, the striking feature is the whiteness of these flowers, like calcoflour-white in the understory.  Only a few regional plants have flowers that stand out as this “white” (such as Platanthera blephariglottis and the introduced Venus’ Flytrap), such that you can spot individuals from a distance based on color alone.

Down on the ground (the tallest plants may reach over 0.5 m), examining flowers, you’ll find a gullet-like, bi-labiate corolla tube – the definition of zygomorphy.  Two upper lobes join to form an emarginate hood over the anthers, while the three lower lobes spread out and down.  You have to peer up into the flower to see the 4 anthers, which pair off, two on top and two below, formed by two long and two short stamens.  The four stamens are sympetalous (their filaments arising from the inner surface of the corolla tube). The upper anthers top the two long filaments attached at the lower base of the tube, while the two lower anthers are formed by shorter filaments originating along the upper side of the corolla tube.  The single style arches amid the anthers, being free from its base to the bifid stigma.  

At the base of the style are 4, very small, pale green, basally-attached mericarps, barely 1 mm tall.  It is, in the end, this unmistakable pistil on which we rest our case that a plant is a mint.  The Lamiales (the Order that includes Mints, Scrophs, Bignons, etc) is rife with plants that have tubular corollas, 4 stamens in pairs, and opposite leaves.  The Mints, however, own the curious 4-parted ovary.  Because the stigma is bifid, we interpret the pistil as having two carpels, each of which is divided into a pair of lobed chambers, united to the style at their bases.  If you find a plant that could be an Acanth, or a Scroph, or a Bignon, but has the four “nutlets” or “mericarps” at the base of the style, then it’s a Mint.

That’s our plant.  A beautiful and distinctive native to the Apalachicola flora.  Rare to encounter, the autecology of the plant has been published in several studies, many supported through various Forest Services.  It should be noted there are other endemic mints in the Florida flora, a, such as Conradina glabra, Stachydeoma graveolens, and Physostegia godfreyi Here are a few studies of Macbridea available on the Web:

Schulze, Dana Madsen, Joan Welker, and Timothy P. Spira, 2002.  Germination and Seed Bank Studies of Macbridea alba (Lamiaceae), a Federally Threatened Plant.  Castanea 67(3): 280-289;    https://www.srs.fs.usda.gov/pubs/ja/ja_schulze001.pdf

Sara A. Johnson,Janice Coons, David N. Zaya, and Brenda Molano-Flores,  2023.  Assessing the Reproductive Ecology of a Rare Mint, Macbridea alba, an Endangered Species Act Protected Species. Plants, 12(7)   https://doi.org/10.3390/plants12071485

Molano-Flores, Brenda, Sara Johnson, and Janice Coons, 2002.  Reproductive ecology of a 

rare Florida endemic mint Macbridea alba.  

Godt, M.J.W., J. Walkerm and J,L. Hamrick, 2004.  Allozyme Diversity in Macridea alba (Lamiaceae), an Endemic Florida Mint, https://www.researchgate.net/journal/The-Journal-of-heredity-0022-1503

Anderson, Chad T., Samantha Dietz, Amy Jenkins, and Jason Drake,  The effects of Fire Season, Frequency, and Forest Structure on the Flowering Abundance of Macbridea alba,  .  Florida Natural Areas Inventory, https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiFnd2R_ff_AhU3q4kEHe2YBaIQFnoECA4QAQ&url=https://www.fnai.org/PDFs/publications/Anderson%20Dietz%20Jenkins%20and%20Drake%202020.pdf&usg=AOvVaw2qlSE_GkOaJxFyH-HMx6gO&opi=89978449

References

Chapman, Alvin W., 1860.  Flora of the Southern United States containing abridged descriptions of the flowering plants and ferns of Tennessee, North and South Carolina, Georgia, Alabama, Mississippi, and Florida: arranged according to the Natural System, 2nd edition, Ivison, Phinney & Co., New York.  Missouri Botanical Garden    https://www.biodiversitylibrary.org/page/6524684 page 325

Nuttall, Thomas,  1818, The genera of North American plants, and a catalogue of the species, to the year 1817, Philadelphia, vol 2. page 36, ( classified along with other mints) Didynamia, Gymnospermia  Source: Missouri Botanical Garden  https://www.biodiversitylibrary.org/page/723779 

Walter, Thomas, 1788. Flora caroliniana : secundum systema vegetabilium perillustris Linnaei digesta; characteres essentiales naturalesve et differentias veras exhibens; cum emendationibus numerous descriptions veras exhibens; cum emendationibus numerosis: descriptionum antea evulgatarum: adumbrationes stirpium plus mille continens: necnon, Generibus novis non paucis, speciebus plurimis novisq ornata.  Autore THOMAS WALTER, Agricola.  J. Wenman, Fleet-street.   Page 162, Didynamia Gymnospermia.  Source: Missouri Botanical Garden.  https://www.biodiversitylibrary.org/page/10001230

Blake, Stephen Fay, 1915.  ‘Some Neglected Names in Walter’s Flora Caroliniana’, Rhodora 17(199): 129-137. Source:  Missouri Botanical Garden.  https://www.biodiversitylibrary.org/page/567476

Elliott, Stephen (LL.D.) 1821, Charleston, Volume I  Source NCSU Libraries  https://www.biodiversitylibrary.org/page/26097584 https://doi.org/10.5962/bhl.title.9508;   1824.  A sketch of the botany of South Carolina and Georgia. in two volumes. Volume II.   https://www.biodiversitylibrary.org/page/26098203; https://doi.org/10.5962/bhl.title.9508.

Glitzenstein, Jeff S., Donna R. Streng, James MacBride, Dale D. Wade, Eric Kjellmark, Patrick McMilland, and Robert K. Peet, 1995.  ‘A Historical Perspective on Longleaf Pine Groundcover Vegetation in the Francis Marion National Forest.’   Proceedings, First Longleaf Pine Alliance Annual Conference, https://www.srs.fs.usda.gov/pubs/ja/1996/ja_1996_wade_001.pdf

Kubes, Amanda J.  2009.  Modeling Species Distributions of Three Endemic Florida Panhandle Mints under Climate Change: Comparing Plant and Pollinator Distribution Shifts under Future Conditions, Master’s Thesis, Florida State University

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