[12][13][11] For more information on the classification of extant lycophytes, see Lycopodiopsida Classification. Species in the genus Leclercqia had fully vascularized microphylls. "The Physiological Resilience of Fern Sporophytes and Gametophytes: Advances in Water Relations Offer New Insights into an Old Lineage." Today, seedless vascular plants are represented by monilophytes and lycophytes. Finally, the fertilized egg will grow a new diploid sporophyte from the diploid zygote of the gametophyte, completing the life cycle. The scientific names and the informal English names used for this group of plants are ambiguous. Please enjoy a free 2-hour trial. . Reproductive morphology of the lycophytes In the lycophytes, some leaves do more than merely photosynthesize. Native Plant Trust or respective copyright holders. If the problem continues, please, An unexpected error occurred. The stem is either underground or aerial. (2016). This adaptation allowed them to transport water, nutrients, and other organic materials, and to attain greater sizeswhich distinguished them from their nonvascular relatives. The living genera are all small herbaceous plants, some erect and others low creepers. lycophyte, (class Lycopodiopsida), class of spore-bearing vascular plants comprising more than 1,200 extant species. Lycopod bark showing leaf scars, from the Middle Devonian of Wisconsin. Mol Phylogenet Evol 19:177186, Yatsentyuk SP, Valiejo-Roman KM, Samigullin TH, Wikstrm TAV (2001) Evolution of Lycopodiaceae inferred from spacer sequencing of chloroplast rRNA genes. New England in 15b, See list of 7 [4] Evo-devo; Selaginella; clubmoss; lycophytes; quillwort; spikemoss; vasculature. Lycophytes reproduce by spores and have alternation of generations in which (like other vascular plants) the sporophyte generation is dominant. Am J Bot 67:274277, Pryer KM, Schneider H, Smith AR, Cranfill R, Wolf PG, Hunt JS, Sipes SD (2001) Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Ann Bot-London 98:679689, Lysk MA, Doleel J (1998) Estimation of nuclear DNA content in Sesleria (Poaceae). Fertilization occurs when a sperm swims to an archegonium. Here we describe morphological traits of living lycophytes and their extinct relatives, consider the molecular underpinnings of trait evolution and discuss future research required in lycophytes to understand the key evolutionary innovations enabling the growth and development of all vascular plants. Most seedless vascular plants produce one type of spore that gives rise to a bisexual gametophyte. Careers. Those that land on a suitable substrate germinate and form a heart-shaped gametophyte, which is attached to the ground by thin filamentous rhizoids. Simplified phylogenetic tree of the animal kingdom, Nobel prizewinning contributions to biology. Please enable it to take advantage of the complete set of features! plants. Base of a fossil lycopsid showing connection with stigmarian roots. (2004). Please check your Internet connection and reload this page. government site. A major cladistic study of land plants was published in 1997 by Kenrick and Crane. More than 20,000 species of ferns live in environments ranging from tropics to temperate forests. Broadly circumscribed group of spore bearing plants, This article is about a broadly defined group of plants that includes the extinct zosterophylls. Final development of the male gametophyte, or microgametophyte, usually occurs on the soil prior to the release of biflagellate sperm. Cytom Part A 51A:127128, Doleel J, Greilhuber J, Suda J (2007) Estimation of nuclear DNA content in plants using flow cytometry. Today, seedless vascular plants are represented by monilophytes and lycophytes. Before Gametophytes are bisexual; i.e., the sperm-producing antheridia and the egg-producing archegonia occur on the same plant. Lycophytes include club mosses, spikemosses, and quillwortsnone of which are true mosses. Unable to load video. Am J Bot 91:15821598, Redondo N, Horjales M, Blanco A (1999) Cantidades de DNA nuclear eporas en Aspleniaceae: AspleniumL. In Selaginella, usually only four large megaspores are produced in a megasporangium. Stems conspicuously jointed, bearing at each joint a small whorl of black or red-brown leaves (sometimes white-margined) that are united at the base; sporangia aggregated in a terminal strobilus [Fig. families Under the terms of the licence agreement, an individual user may print out a PDF of a single entry from a reference work in OR for personal use (for details see Privacy Policy and Legal Notice). BMC Plant Biol 5:10, Wikstrm N (2001) Diversification and relationships of extant homosporous lycopods. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. families Alternation of generations is a feature of all sexually reproducing plants, but the relative size and prominence of the haploid and diploid stages differ among plants. Carboniferous periods are now extinct, but they now exist within the Earth as coal. Leaves and branches come out as whorls from the evenly-spaced joints. families The root systems is always adventitious. Y Polypodium L. Nova Acta Cient Compostel Biol 9:99107, Soltis DE, Soltis PS (1987) Polyploidy and breeding systems in homosporous pteridophyta: a reevaluation. CAS Bot J Linn Soc 90:209216, Nagl W (1978) Endopolyploidy and polyteny in differentiation and evolution. Any member of a clade of vascular plants (sometimes called Monilophyta) based on molecular genetic analysis, comprising the whisk ferns, horsetails, ferns, and their allies such as adders tongues (Ophioglossaceae), moonworts, and grape ferns. Access to the complete content on Oxford Reference requires a subscription or purchase. families Caryologia 20:257264, Bainard JD, Newmaster SG (2010) Endopolyploidy in bryophytes: widespread in mosses and absent in liverworts. In monilophytes, the gametophyte dies off once the sporophyte is firmly established and reaches a large enough size. Monophyletic, paraphyletic, and polyphyletic. In the broadest circumscription of the lycophytes, the group includes the extinct zosterophylls as well as the extant (living) lycophytes and their closest extinct relatives. These gametophytes and sporophytes grow in close contact with the soil and develop rhizoids and root hairs, respectively. Preslia 81:261280, Ekrt L, Holubov TP, Suda J (2010) Species boundaries and frequency of hybridization in the Dryopteris carthusiana (Dryopteridaceae) complex: a taxonomic puzzle resolved using genome size data. Plant Cell Rep 23:203210, Kamierczak A (2010) Endoreplication in Anemia phyllitidis coincides with the development of gametophytes and male sex. 2013. Ann Bot-London 95:807815, Bennett MD (1972) Nuclear DNA content and minimum generation time in herbaceous plants. There was no indication of endoreduplication in any of the leaf, stem, or root tissue analyzed. Unlike nonvascular plants, vascular plantsincluding seedless vascular plantshave an extensive network of vascular tissue comprised of xylem and phloem. Physiol Plantarum 85:625631, Doleel J, Doleelov M, Novk FJ (1994) Flow cytometric estimation of nuclear DNA amount in diploid bananas (Musa acuminata and M. balbisiana). Different sources use varying numbers and names of the extinct orders. 1 ). Representative extinct genera are Lepidodendron and Sigillaria, which were tree lycophytes, and Protolepidodendron, a herbaceous Lycopodium-like plant. families PubMed Flagellated sperm are released and swim on a wet surface to where the egg is fertilized. For example, what most people recognize as a fern is the large, independent fern sporophyte. Ferns, club mosses, horsetails, and whisk ferns are seedless vascular plants that reproduce with spores and are found in moist environments. Plastid Phylogenomics and Plastomic Diversity of the Extant Lycophytes. Sporophytes produce haploid cells called spores through meiosis. 2012 Apr;109(5):851-71. doi: 10.1093/aob/mcs017. Am J Bot 68:881896, Kurth E, Gifford EM (1985) Ontogenetic changes in DNA content in roots of the water fern Azolla filiculoides. This classification is based on the Pteridophyte Phylogeny Group I (PPG I) system, published in 2016. [20], Lycopodites, an early lycopod-like fossil. phylums of this group prefer damp environments, but can also be found in extreme environments (very cold, very dry, etc.) in 14b, See list of 2 Underground stems known as rhizomes anchor the plants to the ground. In most animals, only the diploid stage is multicellular, and gametes are the only haploid cells. Plant Sci 165:933939, Kamierczak A (2004) Aminooxyacetic acid inhibits antheridiogenesis and development of Anemia phyllitidis gametophytes. Bot J Linn Soc 164:1015, Polito VS (1980) DNA microspectrophotometry of shoot apical meristem cell populations in Ceratopteris thalictroides (Filicales). The lycophytes, when broadly circumscribed, are a group of vascular plants that include the clubmosses. and Grev. Lycophytes are vascular plants that have true roots, are sporophyte dominant, and have microphylls. Here we describe morphological traits of living lycophytes and their extinct relatives, consider the molecular underpinnings of trait evolution and discuss future research required in lycophytes to understand the key evolutionary innovations enabling the growth and development of all vascular plants. Plant Cell Environ 23:657663, Freeberg JA, Gifford EM (1984) The root apical meristem of Osmunda regalis. Share. Lycopodium dendroideum, a modern member of the Lycopodiales, Isoetes melanospora, a modern member of the Isoetales, Restoration of Pleuromeia, an extinct Isoetales genus from the Early Triassic. - 91.234.33.200. Their preferred cladogram shows the zosterophylls and associated genera basal to both the lycopodiopsids and the euphyllophytes, so that there is no clade corresponding to the broadly defined group of lycophytes used by other authors. Please enter an institutional email address. Caryologia 21:8389, De Veylder L, Beeckman T, Inz D (2007) The ins and outs of the plant cell cycle. Deep origin and gradual evolution of transporting tissues: Perspectives from across the land plants. FOIA We here report on a new, clade-specific group II intron in the rps1 gene of monilophytes (ferns). Bringing the multicellular fern meristem into focus. Australian Institute of Agricultural Science, Sydney, pp 8793, Wagner WH (1954) Reticulate evolution in the Appalachian Aspleniums. in 6b, See list of 3 Ferns, horsetails (often treated as ferns), and lycophytes (clubmosses, spikemosses, and quillworts) are all pteridophytes. Can J Bot 60:13601370, Kurth E (1982) Mitotic activity in the root apex of the water fern Marsilea vestita Hook. et al. Plant Biol 8:770777, Grime JP, Mowforth MA (1982) Variation in genome sizean ecological interpretation. However, unlike bryophytes, ferns have a dominant sporophyte generation that is diploid. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Seedless Vascular Plants Were the First Tall Plants on Earth. The Gibberellin perception system evolved to regulate a pre-existing GAMYB-mediated system during land plant evolution. Caryologia 52:123132, Manton I (1950) Problems of cytology and evolution in the Pteridophyta. Upper left: This page was last edited on 9 April 2023, at 08:14. donations to help keep this site free and up to date for Am J Bot 72:16761683, Little DP, Moran RC, Brenner ED, Stevenson DW (2007) Nuclear genome size in Selaginella. While most ferns form large leaves and branching roots, the whisk ferns, Class Psilotopsida, lack both roots and leaves, which were probably lost by reduction. The members of one of the chief living families, Lycopodiaceae, are homosporous (with just one kind of spore). Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada, N1G 2 W1, Jillian D. Bainard,Thomas A. Henry,Luke D. Bainard&Steven G. Newmaster, You can also search for this author in families An official website of the United States government. The yellow to brown underground plant may become carrot-shaped, rod-shaped, or disk-shaped and 1 to 2 centimetres (0.4 to 0.8 inch) in length or width. In Isoetes, sporangia are produced at the expanded concave bases of the quill-like leaves. [citation needed], Within the broadly defined lycophyte group, species placed in the class Lycopodiopsida are distinguished from species placed in the Zosterophyllopsida by the possession of microphylls. Jillian D. Bainard. Legal. Zosterophylls and extant lycophytes are all relatively small plants, but some extinct species, such as the Lepidodendrales, were tree-like, and formed extensive forests that dominated the landscape and contributed to the formation of coal.[6]. Today, seedless vascular plants are represented by lycophytes and monilophytes. 2022 Aug 29;190(1):100-112. doi: 10.1093/plphys/kiac313. Less than 1% of known monilophytes and lycophytes have a genome size estimate, and substantially less is known about the presence and prevalence of endopolyploid nuclei in these groups. Conservation and divergence of small RNA pathways and microRNAs in land plants. The term "fern ally" included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns (Marsileaceae, Salviniaceae and Ceratopteris), and even a much wider range of taxa. Bot J Linn Soc 140:169173, Haufler CH (1987) Electrophoresis is modifying our concepts of evolution in homosporous pteridophytes. Frangedakis E, Saint-Marcoux D, Moody LA, Rabbinowitsch E, Langdale JA. External mold of Lepidodendron from the Upper Carboniferous of Ohio. Blood Cell Mol Dis 27:830843, Greilhuber J (1988) Self-tanninga new and important source of stoichiometric error in cytophotometric determination of nuclear DNA content in plants. However, the monophyletic status of monilophytes and the placement of sphenophytes (horsetails) well within the extant monilophyte clade provide insights . "Pteridophyta" is thus no longer a widely accepted taxon, but the term pteridophyte remains in common parlance, as do pteridology and pteridologist as a science and its practitioner, respectively. Collectively, ferns belong to a group known as monilophytes. 2023 Springer Nature Switzerland AG. In: Lewis WH (ed) Polyploidy, biological relevance: Proceedings of the International Conference on Polyploidy, Biological Relevance. When we say ferns, we are talking about leptosporangiate ferns unless. The seedless vascular plants were the first to evolve specialized vascular systemsan adaptation that helped them become the first tall plants on Earth. Monilophytes, like lycophytes, are all spore bearing and ''seed-free.'' Because of this, members of these two lineages were traditionally lumped under various terms, such as ''pte- Branching is usually dichotomous; that is, the shoot tip forks repeatedly. Some of these microphylls were several feet long! The root systems is always adventitious. If you have any questions, please do not hesitate to reach out to our customer success team. Historically both lycophytes and monilophytes were grouped together as pteridophytes (ferns and fern allies) on the basis of being spore-bearing ("seed-free"). creates the strength and stiffness of the wall. The phylum Lycopodiophyta consists of close to 1,200 species, including the quillworts (Isoetales), the club mosses (Lycopodiales), and spike mosses (Selaginellales), none of which are true mosses or bryophytes. "Overlapping Patterns of Gene Expression Between Gametophyte and Sporophyte Phases in the Fern Polypodium Amorphum (Polypodiales)." Google Scholar, Bennert W, Lubienski M, Krner S, Steinberg M (2005) Triploidy in Equisetum subgenus Hippochaete (Equisetaceae, Pteridophyta). The consensus classification produced by the Pteridophyte Phylogeny Group classification in 2016 (PPGI) places all extant (living) lycophytes in the class Lycopodiopsida. Group 1: Lycophytes, Monilophytes. For the group excluding the zosterophylls, see, "The origin and early evolution of plants on land", Archaeal Richmond Mine acidophilic nanoorganisms, https://en.wikipedia.org/w/index.php?title=Lycophyte&oldid=1148956644, Short description is different from Wikidata, Articles with unsourced statements from October 2019, Creative Commons Attribution-ShareAlike License 3.0. lycophyte: a tracheophyte subdivision of the Kingdom Plantae; the oldest extant (living) vascular plant division at around 410 million years old sporangia: enclosures in which spores are formed Ferns and Other Seedless Vascular Plants Water is required for fertilization of seedless vascular plants; most favor a moist environment. Learn more about Institutional subscriptions, Aagard SMD, Vogel JC, Wikstrm N (2009) Resolving maternal relationships in the clubmoss genus Diphasiastrum (Lycopodiaceae). These divisions may occur before the spores are shed from the microsporangium. Annual Review of Plant Biology, 60, 223-38. For example, "Lycopodiophyta" and the shorter "Lycophyta" as well as the informal "lycophyte" may be used to include the extinct zosterophylls or to exclude them. Plant Cell Environ 26:571584, Article The lycophytes, when broadly circumscribed, are a group of vascular plants that include the clubmosses. families in 20b, See list of 2 The sexuality of pteridophyte gametophytes can be classified as follows: These terms are not the same as monoecious and dioecious, which refer to whether a seed plant's sporophyte bears both male and female gametophytes, i. e., produces both pollen and seeds, or just one of the sexes. The remains of Lepidodendron and other extinct lycophytes form most of the great coal beds of the world. Phyllitis Hill Ceterach Willd. Russ J Genet 37:10681073. In order to begin, please login. Monilophytes ferns, horsetails, whisk ferns Have independent gametophyte and sporophyte generations. 2023 Feb 8;24(4):3352. doi: 10.3390/ijms24043352. Course Hero is not sponsored or endorsed by any college or university. They have terrestrial or subterranean gametophytes that vary in size and shape depending on the genera. Each photo represents one family in this group. The leaves are generally small, although they sometimes achieved a length of one metre (three feet) in the gigantic Lepidodendron. It took another 50 years or so before botanists realised that clubmosses and spikemosses were distinct . A cluster of organized sporangia is called a strobilus (cone). Lycophyte, (class Lycopodiopsida), class of spore-bearing vascular plants comprising more than 1,200 extant species. Sorry, your email address is not valid for this offer. The names and ranks used for this group vary considerably. Aya, K., Hiwatashi, Y., Kojima, M., Sakakibara, H., Ueguchi-Tanaka, M., Hasebe, M., & Matsuoka, M. (2011). These final stages in development usually occur on the soil after the megaspore with the enclosed female gametophyte is shed from the megasporangium. [2][3] Lycophytes were some of the dominating plant species of the Carboniferous period, and included the tree-like Lepidodendrales, some of which grew over 40 metres (130ft) in height, although extant lycophytes are relatively small plants.[4]. Disclaimer. in 7a, See list of 2 To elucidate the evolution of vascular development and leaf formation, molecular studies using RNA Seq, quantitative reverse transcription polymerase chain reaction, in situ hybridisation and phylogenetics have revealed the diversification and expression patterns of KNOX, ARP, HD-ZIP, KANADI, and WOX gene families in lycophytes. families In some species the gametophyte becomes a small, green plant with numerous lobes, growing on the surface of the soil; the time interval between spore germination and sexual maturity of the gametophyte may be eight months to a year. 2017 Oct;216(2):591-604. doi: 10.1111/nph.14318. sharing sensitive information, make sure youre on a federal [Source], Pittermann, Jarmila, Craig Brodersen, and James E. Watkins. in 19b, See list of 3 [1] Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In land plants, genetic resources are well established in model species representing lineages including bryophytes (mosses, liverworts, and hornworts), monilophytes (ferns and allies), and seed plants (gymnosperms and flowering plants), but few resources are available for lycophytes (club mosses, spike mosses, and quillworts). The extinct zosterophylls have at most only flap-like extensions of the stem ("enations") rather than leaves, whereas extant lycophyte species have microphylls, leaves that have only a single vascular trace (vein), rather than the much more complex megaphylls of other vascular plants. Would you like email updates of new search results? families In: Thomson JA, Smith RT (eds) Bracken biology and management. families 25 ], borne on the underside of peltate sporangiophores. Please enter your Institution or Company email below to check. Club mosses, which are the earliest form of seedless vascular plants, are lycophytes that contain a stem and microphylls. in 18b, See list of 4 families However, like nonvascular plants, seedless vascular plants reproduce with spores rather than seeds. If you need immediate assistance, please email us at subscriptions@jove.com. J Hered 52:139144, Partanen CR (1965) On the chromosomal basis for cellular differentiation. families Monilophytes include ferns, horsetails, and whisk ferns and their relatives. At the gametophyte stage - which is typically very small and found on or just below the soil surface - haploid gametes are formed by mitosis. National Library of Medicine There are three major groupings covering the plant life on Earthnonvascular plants,seedless vascular plants, and seed plants. families If that doesn't help, please let us know. The embryo, or young sporophyte, consists of a shoot, a root, and a food-absorbing outgrowth called a haustorial foot. New Phytologist, 210(3), 790-793. The club mosses, or phylum Lycopodiophyta, are the earliest group of seedless vascular plants. [9][10] English names, such as "lycophyte", "lycopodiophyte" or "lycopod", are similarly ambiguous, and may refer to the broadly defined group or only to the extant lycophytes and their closest extinct relatives. Pteridophytes (ferns and lycophytes) are free-sporing vascular plants that have a life cycle with alternating, free-living gametophyte and sporophyte phases that are independent at maturity. Synapomorphy: microphylls. All rights reserved, Chapter 5: Membranes and Cellular Transport, Chapter 12: Classical and Modern Genetics, Chapter 22: Circulatory and Pulmonary Systems, Chapter 28: Population and Community Ecology, Chapter 29: Biodiversity and Conservation, Chapter 34: Plant Structure, Growth, and Nutrition, Chapter 36: Plant Responses to the Environment. A JoVE representative will be in touch with you shortly. [8][6] The name "Lycopodiophytina" has also been used in the inclusive sense. [3], Furthermore, within the Polypodiopsida, the largest grouping, a number of informal clades were recognised, including leptosporangiates, core leptosporangiates, polypods (Polypodiales), and eupolypods (including Eupolypods I and Eupolypods II). Our editors will review what youve submitted and determine whether to revise the article. Author of. Journal of Botany 2010:7 pages doi:10.1155/2010/316356, Bainard JD, Fazekas AJ, Newmaster SG (2010) Methodology significantly affects genome size estimates: quantitative evidence using bryophytes. families Like animals, seedless vascular plants (and other plants) alternate between meiosis and fertilization during reproduction. This sister relationship offers a unique opportunity to study the conservation of traits such as sporophyte branching, vasculature, and indeterminacy, as well as the convergent evolution of traits such as leaves and roots which have evolved independently in each vascular plant lineage. The diploid sporophyte is the most conspicuous stage of the life cycle. If you would like to continue using JoVE, please let your librarian know as they consider the most appropriate subscription options for your institutions academic community. Caryologia 18:383394, DAmato F, Avanzi S (1968) The shoot apical cell of Equisetum arvense, a quiescent cell. in 22b. Augstein, F., & Carlsbecker, A. The sporangia (spore cases) occur singly on the adaxial side (the upper side facing the stem) of the leaf. Am J Bot 69:464473, Gifford EM, Kurth E (1983) Quantitative studies of the vegetative shoot apex of Equisetum scirpoides. [16][17] The genus Renalia illustrates the problems in classifying early land plants. Their leaves are reduced and non-photosynthetic. Updates? In seedless vascular plants (as well as seed plants), the diploid stage of the life cyclethe sporophyteis dominant. For questions on access or troubleshooting, please check our FAQs, and if you can''t find the answer there, please contact us. Federal government websites often end in .gov or .mil. Let us know if you have suggestions to improve this article (requires login). The big difference between monilophytes and lycophytes: In the monilophyte life cycle, the sporophyte and gametophyte are. Their other common characteristics include vascular plant apomorphies (e.g., vascular tissue) and land plant plesiomorphies (e.g., spore dispersal and the absence of seeds). Can you please help us? Ann Bot-London 82(Suppl A):1726, Doleel J, Barto J, Voglmayr H, Greilhuber J (2003) Nuclear DNA content and genome size of trout and human. (2006), the first higher-level pteridophyte classification published in the molecular phylogenetic era, considered the ferns as monilophytes, as follows:[3], where the monilophytes comprise about 9,000 species, including horsetails (Equisetaceae), whisk ferns (Psilotaceae), and all eusporangiate and all leptosporangiate ferns. in 3b, See list of 17 [clarification needed] This is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate for non-leptosporangiate ferns. All rights reserved. Lycophytes sometimes have sporangia clustered at the tips of the branches, forming _. Getting to the roots: A developmental genetic view of root anatomy and function from Arabidopsis to Lycophytes. The spores are haploid, and are dispersed by structures called sori, clustered on the underside of the leaves. It has characteristics both of the non-lycophyte rhyniophytes terminal rather than lateral sporangia and of the zosterophylls kidney-shaped sporangia opening along the distal margin. Whisk ferns were considered an early pterophytes. Evolution 8:103118, Wagner WH (1955) Cytotaxonomic observations on North American ferns. Overtopping growth occurs when the different branches of a plant differentiate and. Ferns and lycophytes are two groups of vascular plants without wood, seeds or flowers. The two major groups previously included in Pteridophyta are phylogenetically related as follows:[7][8][9], Pteridophytes consist of two separate but related classes, whose nomenclature has varied. Fronds fulfill a double role; they are photosynthetic organs that also carry reproductive structure. Nature Communications, 2(1), 544-549. MeSH Fill the form to request your free trial. We use cookies to enhance your experience on our website. Physiol Plantarum 138:321328, Knight CA, Beaulieu JM (2008) Genome size scaling through phenotype space. This intron, rps1i25g2, is strikingly similar to rpl2i846g2 previously identified in the mitochondrial rpl2 gene of seed plants, ferns, and the lycophyte Phlegmariurus squarrosus. Discover thousands of Definite strobili are formed in Selaginella, and the sporophylls generally differ from the vegetative leaves, although not as much as in the species of Lycopodium that form strobili. Therefore, pteridophytes do not form a clade but constitute a paraphyletic grade. Lycophytes can be homosporous or heterosporous. These organisms __________ have tracheids, and they ___________ botanically, Spring 16 BSC2011 Exam 1 Bio+ Weekly Update 2016.

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