Ferns belong to the group Pteridophyta, along with Psilotophyta, Equisetophyta, Polipodiophyta and Lycopodiophyta. (Palacios, 1986). These originated approximately 450 million years ago (Mendoza-Ruiz and Ceja-Romero, 2014). During the Carboniferous these divisions reached their maximum development, although they later went through a regression that allowed them to endure over time. (Cited in Dimas, Ruelas & Curiel, 1994).
Ferns are vascular plants that have an alternation of generations, with the diploid and asexual sporophyte being the predominant one, the plant as such. This is composed of a stem that is sometimes branched, it may present adventitious roots originating from the endodermis, rhizome and leaves (fronds). They have variable sizes: from a few centimeters (genus Azolla) to several meters, like tree ferns. Its development ranges from the formation of an embryo through syngamy, that is, the union of the antherozoid and the oosphere (the male and female reproductive structures, respectively), to the formation of spores (Velázquez & Aguirre, 2015). The spores are found in the structures (sori) behind the leaf. You can see them in figures 1, 2, 3 and 4.
The gametophyte (we do not usually observe this stage of the fern's life with the naked eye) is haploid and sexual. Its development starts from the formation of spores by meiosis, until the formation of mature sexual cells. Its main characteristics are the size and place of development: a few microns if they develop inside the spores (heterosporic ferns), up to one or two centimeters and cordate and if they develop outside of these, homosporic ferns (Velázquez and Aguirre, 2015).
Dirzo and Raven (1994) proposed that the increasing modification of the natural communities and the floristic richness of Mexico make it necessary to carry out a complete biological inventory. To carry out these inventories, the exploration, collection and herbalization of specimens is essential.
In the case of collecting ferns, it is necessary to select fronds that have developed sporangia: they can appear as black, brown or powdery spots on the underside of the leaf. Each specimen must have the apex, base of the stipe and the associated scales; a rhizome without soil, mosses or foreign materials. After collection, the specimens must be pressed, showing special interest in ensuring that the fronds reveal the abaxial (front) and adaxial (back) faces; They should be dried as soon as possible to prevent the fronds from wilting.
Rzendowski (1991) pointed out that Mexico and Central America are regions that have a great diversity of plant organisms. (Cited in Arreguín et al., 2009). Palacios (1986) mentioned that it is the diversity in climates and topography that favors the presence and abundance of species in our country. Mendoza-Ruiz and Pérez-García (2009) indicated that in the Mexican territory there are around 1014 species of ferns and lycophytes, most of which are considered common and with a very wide distribution. These constitute a proportion between 10 and 12% of the pteridophytes existing in the world. (Arreguín et al. 2009).
Arreguín and his collaborators, in 2009, stated that 54% of species are found in the mountain cloud forest; 45% in coniferous forest; 33.6% in Quercus forest; 34.5% in grasslands; 28% xeric scrub; 22% in pine-oak forest; 3.5% in oak scrub and 1.8% as aquatic and halophilic vegetation.
The states of the country that have the greatest number of species are: Oaxaca with 690, Chiapas with 609 and Veracruz with 572 species (Vázquez et al. 2006).
Here we show you some species of ferns that are found in a very curious forest in the state of Puebla.
Asplenium monanthes
They are terrestrial and epiphytic plants that have a short rhizome, the fronds are erect, 35 to 65 cm long and 3.5 cm wide (Sánchez et al. 2008), pinnate, the blade regularly has 20 to 30 pairs of pinnae, although it can present up to 50 pairs of rectangular pinnae, reduced at the base of the blade, with sub-entire teeth, it frequently produces sori, one or two per pinna, protected by an elongated lateral indusium (Rodríguez et al. 2009) that measures from 2 to 5mm long by 1mm wide. The spores are monoletes, light brown in color, that measure 33 to 44 m long by 23.6 to 34.6 m wide (Sánchez et al. 2011).
The gametophyte has a typical chordate shape, has abundant rhizoids, measures approximately 520.2 m in length by 346.8 m in width, and is normally made up of 85 cells. The antheridia are found in the lower part of it, near the rhizoids, they produce more than 50 antherozoids. The archegonia are found at the top of the gametophyte in the notch, are ovate in shape, develop after the antheridia and are larger; They are made up of eight neck cells, three of the neck canal, a ventral cell and the ovocell (Sánchez et al. 2008).
They live mainly in pine-oak forests, in high places, on the American continent it extends from Arizona through Mexico to South America (Rodríguez and Kiessling, 2012).
Adiantum poiretii
It has a short, creeping rhizome, stipes straw-colored, smooth, shiny, 20 to 22 cm. of length; bipinnate, abovado-lanceolate fronds, 20 cm. long by 10 wide; pinnules thin, herbaceous, cuneate at the base and rounded in its upper contour, fanned-quadri-quinti-lobed, not toothed; relatively large, yellow sori at the bottom of the sinus; indusios slender, reniform, membranous.
Dryopteridaceae: Dryopteris.
Dryopteridaceae is a family of leptosporangiate ferns (Hong, M. et al. 2007), it has 60 genera that include 3000 species. The genus Dryopteris is mainly found in temperate forests of the northern hemisphere (Zhang et al. 2012) and in mountainous areas of the tropics (Yatskievych, 2008).
It contains 225 to 300 species worldwide. They are terrestrial, rock-growing and epiphytic plants. The sporophyte is perennial, it has a short and robust rhizome, its stem is erect and sometimes branched, the petioles usually have scales, its fronds are 1 to 5 times pinnate (Munro, 2014). Although leaf morphology is highly variable, the sori are commonly round with indusio. The spores are ellipsoidal monoliths of dark brown color, rugulate with wide, rounded walls, protected by a reniform indusium.
The gametophyte is of a typical chordate shape, it has rhizoids, the antheridia are found in the lower part of the gametophyte and the archegonia in the upper part, in the notch and are larger than the antheridia.
Family Blechnaceae
This family belongs to the leptosporangiate ferns (Class Polypodiopsida, Subclass Polypodiidae, Order Polypodiales), nine or ten genera and 220-250 species are recognized. It has a cosmopolitan distribution, but the greatest diversity is found in the southern hemisphere, in tropical and subtropical ecosystems.
It is composed of occasionally scandent terrestrial or epilitic ferns of small to large sizes. Well-developed petiole, sucate adaxially, vascular bundles that present a U-shaped pattern. The blade is usually pinnate, with entire to pinnatifid cones, less frequently they are simple or lobed. The rachis is furrowed adaxially. The sori in the secondary veins appear discrete or forming continuous cenosores, they may or may not present an indusium and the sporangia present a longitudinal ring of many cells.
Woodwardia
It is a terrestrial genus, with monomorphic fronds. The rhizomes are creeping, erect or decumbent. The fronds are lanceolate, oblong-lanceolate, ovate-lanceolate, rarely simple, pinnatifid, pinnate-pinnatifid or bipinnatifid. Veins anastomosed, forming regular areolas along the coast and costulas. Discreet soros, sunk in the sheet.
What is your favorite fern?
References
Arreguín-Sánchez et al. (2009, August). Analysis of the distribution of fern and related species in the Valley of Mexico, ecological and floristic notes. Polybotany: 15-36, ISSN 1405-2768; 28, pp. 15-36.
Hong, M., Xian, C., Wei, W., Yin, L., & Zhi, D. (2007). Molecular Phylogeny of the Fern Family Dryopteridaceae Inferred from Chloroplast rbcL and atpB Genes. International Journal of Plant Sciences. The University of Chicago Press, 168 (9): 1311-1323.
Mendoza-Ruiz, A. & J. Ceja-Romero. (2014). Atlas of bryophytes and pteridophytes. Metropolitan Autonomous University, Iztapalapa. 1st edition, Mexico, D. F. 124 pp.
Mendoza-Ruiz & Pérez-García. (2009). Ferns and Lycopodia from Mexico. Mexico: National Commission for the Knowledge and Use of Biodiversity.
Munro, G. (2014). Not a Type of Dryopteris tetrapinnata W.H.Wagner & Hobdy (family dryopteridaceae). Herbarium Pacificum Bishop Museum (BISH), BISH1017293. GlobalPlants. JSTOR.
Palaces. (1986). Pteridology in Mexico. Metropolitan Autonomous University, Iztapalapa. No. 116.
Rodríguez, R. and Kiessling, A. (2012). Asplenium monanthes L. ECOS LTDA. Chili. (pp. 1-6).
Sánchez, L., Arreguín, M. and Fernández, R. (2008). Gametophytes and young sporophytes of two pteridophytes: Asplenium monanthes L. and Elaphoglossum minutum. Polybotany, 25, pp. 29-43, ISSN 1405-2768.
Vázquez Torres, Mario, Campos Jiménez, Jaqueline, Cruz Pérez, Alfredo. Ferns and related plants of the Banderilla mountain cloud forest, Veracruz, Mexico. Polibotany [online] 2006, (November: [Consultation date: December 1, 2023]
Velázquez, H. and Aguirre, E. (2015). Ferns as ornamental plants. Use of Mexican plants. Science. Mexico (pp. 24-31).
Yatskievych, G. (2008). A New Species And Three Generic Transfers In The Fern Genus Notholaena (pteridaceae). Novon A Journal for Botanical Nomenclature. 18:120-124.
Zhang, Li-Bing, Liang, Zhang, Shi-Yong Dong, Emily B Sessa, Xin-Fen Gao y Atsushi Ebihara. (2012). Molecular circumscription and major evolutionary lineages of the fern genus Dryopteris (Dryopteridaceae). BMC Evolutionary Biology. China 12:180 (pp. 1-15).