''Lygodium palmatum'' is the only species of its genus native to

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. Unlike most species in the genus, this one, called the American climbing fern, Hartford fern (after

Hartford, Connecticut Hartford is the List of capitals in the United States, capital city of the U.S. state of Connecticut. The city, located in Hartford County, Connecticut, Hartford County, had a population of 121,054 as of the 2020 United States census, 2020 ce ...

), or Alice's fern, is extremely hardy in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

zones (other species tolerant of temperate climates include New Zealand's '' Lygodium articulatum'' and the Japanese ''

Lygodium japonicum ''Lygodium japonicum'' is a species of fern that is known by the common names vine-like fern and Japanese climbing fern. It is native to eastern Asia, including Taiwan, Japan, Korea, southeastern Asia, and India, and eastern Australia. The fern i ...

'', which is now highly invasive in Florida).The name "Hartford Fern" being derived from its former prevalence in Hartford and the surrounding Connecticut area. It was extensively used as a Christmas decoration by early settlers, leading to the first law protecting a plant species in the United States in 1869. This fern is on endangered or threatened species lists in several states. It requires constant moisture, high light levels, and intensely

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

soil to thrive. Where these conditions are present, it grows in abundance. This leads to a pattern of abundant, but rare and localized populations throughout its range. Its range is essentially

Appalachia Appalachia ( ) is a geographic region located in the Appalachian Mountains#Regions, central and southern sections of the Appalachian Mountains in the east of North America. In the north, its boundaries stretch from the western Catskill Mountai ...

n, ranging from

New England New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...

down through the Appalachians,

Piedmont Piedmont ( ; ; ) is one of the 20 regions of Italy, located in the northwest Italy, Northwest of the country. It borders the Liguria region to the south, the Lombardy and Emilia-Romagna regions to the east, and the Aosta Valley region to the ...

and Appalachian plateaus into the American south. Like other rare ''Lygodium'' species (such as '' Lygodium articulatum''), their spores have a relatively meager viability, with even immediately sown spores having less than a 50% germination rate, and spores sown after 6 months of storage having less than 5%.

Taxonomy

''Lygodium palmatum'' is generally accepted to be part of a clade of basally divergent members of the Ly''godium'' genus.Some modern systematists have placed it as the sole member of a basally divergent subgenus ''Palmata'', while others have placed it in a clade with '' Lygodium articulatum''. The divergence of these results is likely due to the differential out group selection of the two studies. This divergence is evidenced both by molecular phylogenetics, and by various morphological discrepancies between ''Lygodium palmatum'' and the remainder of the genus. Most notably, their spores are substantially smoother than any other species in the genus, and they possess dichotomously branched pinnae, and high levels of

frond dimorphism Frond dimorphism refers to a difference in ferns between the fertile and sterile fronds. Since ferns, unlike flowering plants, bear spores on the leaf blade itself, this may affect the form of the frond itself. In some species of ferns, there is v ...

. Interestingly, even within the limited present range of the species, there are regional differences that some argue may constitute subspecies. Of particular note is the divergence in the character of hairs on the abaxial surface of pinnae - they are largely glabrous in specimens found Northeast of Maryland, and are pubescent in those Southwest of Maryland, and in isolated populations found in Ohio and Michigan. ''Lygodium palmatum'' has a basal chromosome count of n=30, as is common among the genus, with the other common ploidy levels being n=28 and 29.

References

*Lellinger, David B. ''A Field Manual of the Ferns & Fern Allies of the United States & Canada''. Smithsonian Institution, Washington, DC. 1985.

External links

* palmatum {{Polypodiidae-stub