Hubbry Logo
LiguleLiguleMain
Open search
Ligule
Community hub
Ligule
logo
7 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Ligule
Ligule
Ligule
View on Wikipedia
from Wikipedia

A ligule (from Latin: ligula "strap", variant of lingula, from lingua "tongue") is a thin outgrowth at the junction of leaf and leafstalk of many grasses (family Poaceae) and sedges (family Cyperaceae). A ligule is also a strap-shaped extension of the corolla, such as that of a ray floret in plants in the daisy family Asteraceae.[1]

Look up ligule in Wiktionary, the free dictionary.

Poaceae and Cyperaceae

[edit]

The ligule is part of the leaf that is found at the junction of the blade and sheath of the leaf. It may take several forms, but it is commonly some form of translucent membrane or a fringe of hairs. The membranous ligule can be very short 1–2 mm (Kentucky bluegrass, Poa pratensis) to very long 10–20 mm (Johnson grass, Sorghum halepense), it can also be smooth on the edge or very ragged. Some grasses do not have a ligule, for example barnyardgrass (Echinochloa crus-galli).

A ligule can also be defined as a membrane-like tissue or row of delicate hairs typically found in grasses at the junction of the leaf sheath and blade. The ligule appears to be a continuation of the leaf sheath and encircles or clasps the stem as does the leaf sheath. The three basic types of ligules are: membranous, a fringe of hairs (ciliate), and absent or lacking. Most grasses have ligules, and the shape, length, and appearance of the ligule margin provide consistent characters for separating genera and some species of grasses.

Ligulate floret, typical for flowers of some members of the family Asteraceae:
A. ovary
B. pappus
C. theca
D. ligule
E. style with stamen

In grass-like plants such as sedges (Cyperaceae) and rushes (Juncaceae), ligules are usually absent or poorly developed.[citation needed]

Asteraceae

[edit]
Further information: Ray flower

In members of Asteraceae, a ligule is the elongated tongue of the corolla of a ray flower or ligulate flower.[2]

Lycopodiopsida

[edit]

The microphylls of Lycopodiophyta of the heterosporous families Selaginellaceae (spikemosses or lesser clubmosses) and Isoetaceae (quillworts) have minute, scale-like flaps of tissue called ligules at the base of the upper surface of each leaf blade. This feature distinguishes them from the family Lycopodiaceae (clubmosses). It is assumed to have originated at least 408 million years ago, and is multicellular in origin in spikemosses and unicellular in origin in quillworts.[3]: 7 [4]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Ligule

View on Grokipedia
from Grokipedia
A ligule is a thin, strap-like or membranous outgrowth occurring in various taxa, most prominently as a protective at the junction between the leaf blade and sheath in the (grasses) and (sedges), a tongue-shaped structure on the adaxial surface of microphylls in lycophytes such as , and the flattened, petaloid extension of the corolla in ray (ligulate) florets of the family. The term 'ligule' derives from Latin ligula ('little tongue'), reflecting its strap- or tongue-like form. In grasses and sedges, the ligule arises from the inner of the leaf sheath and varies in form from a membranous scale to a fringe of hairs, traditionally regarded as a barrier against , particles, and fungal spores entering the leaf axis. Recent ultrastructural analyses reveal cytochemical evidence of secretory activity in ligules of species like , including abundant and Golgi-derived vesicles, suggesting roles in active protection or lubrication beyond passive shielding. Ligules are taxonomically significant for identifying grass genera, with their morphology—such as length, texture, and presence of auricles—used in keys for species differentiation. In lycophytes, particularly the genus , the ligule is a small, basally positioned outgrowth on each microphyll and , consisting of a three-zoned body with meristematic, , and senescent regions that develop complex cellular features like agranal plastids and lomasomes. These ligules exhibit diverse shapes, including linguiform, campanulate, and flabellate forms across species, and may facilitate of extracellular materials through vesicle discharge, potentially aiding in water retention or sporangial protection during the plant's heterosporous life cycle. Ligules are characteristic of certain lycophytes, such as and , distinguishing these subgroups from other vascular plants and studied for evolutionary homology to tissues. Within the , the ligule denotes the strap-shaped, five-toothed limb of the corolla in ligulate florets, which form the colorful ray flowers in capitula (flower heads) of many , enhancing visual attractants for . This structure is characteristic of tribes like , where entire heads may consist solely of ligulate florets, and contrasts with tubular disk florets in the center, contributing to the family's deceptive "single flower" appearance that promotes efficient . Ligules in are evolutionarily derived from bilabiate corollas and vary in length and pigmentation, influencing in approximately 25,000 worldwide.

Introduction and Definition

Definition

A ligule is a thin, strap-like or membranous outgrowth occurring in various plant taxa, most prominently as a protective at the junction between the leaf blade and sheath in the (grasses) and (sedges), a tongue-shaped structure on the adaxial surface of microphylls in lycophytes such as , and the flattened, petaloid extension of the corolla in ray (ligulate) florets of the family. In grasses and sedges, this appendage arises from the inner of the leaf sheath and varies in form from a smooth membrane to a fringe of hairs. The term "ligule" originates from the Latin ligula, meaning "little tongue," and its first botanical application dates to the , when described it as a unique structure in grasses, distinguishing it as part of the leaf's tripartite organization comprising the sheath, ligule, and . Early uses emphasized its role as a diagnostic character for grass , with subsequent refinements in the clarifying its morphological origins. Importantly, the ligule must be distinguished from similar appendages such as auricles, which are paired, ear-like lateral projections occurring at the same sheath-blade junction in select grasses but arising from the blade base rather than the sheath interior. It also differs from stipules, which are typically paired, leaf-like or scale-like structures at the base of the petiole in many dicotyledons, functioning primarily in protection rather than marking a sheath-blade transition. Ligules are particularly characteristic of families such as , , and , as well as lycophytes in the class .

Etymology and Terminology

The term "ligule" originates from the Latin word ligula, a form of lingua meaning "," thus denoting a "little " or "," which aptly describes the strap-like or tongue-shaped outgrowth it refers to in botanical contexts. This etymological root reflects the structure's morphological resemblance to a small, projecting . In English botanical , the term first appeared around 1847, though conceptual descriptions of similar structures date back to the early in works discussing grass anatomy, with initial definitions emerging between 1800 and 1834. In older botanical texts, the spelling "ligula" was commonly used interchangeably with "ligule," particularly in translations from Latin or New Latin sources, though "ligule" became the standardized English form by the mid-19th century. To avoid confusion, it is important to distinguish the botanical ligule from its zoological counterpart; in , ligula refers to a spoon- or strap-shaped component of the (lower ) in , serving functions like licking or feeding, but sharing the same Latin etymology without implying structures. For contextual understanding, related botanical terms include the leaf blade (also called lamina), which is the broad, flattened, photosynthetic portion of a leaf; the sheath, a tubular extension at the base of certain leaves (especially in grasses) that envelops the stem; and the petiole, the slender stalk connecting the leaf blade to the stem in many . These elements provide prerequisite anatomy for ligule placement, typically at the junction of the blade and sheath.

Morphology and Structure

General Morphology

Ligules are thin, strap-like or membranous outgrowths that arise from diverse structures across groups, serving as analogous morphological features rather than homologous ones. In and , they occur at the junction between the sheath and , typically as translucent membranous flaps or fringes of hairs composed primarily of epidermal cells, extending from the inner surface of the sheath and partially encircling the stem. In lycophytes like , ligules are tongue-shaped appendages on the adaxial surface of microphylls, while in , they form the flattened, petaloid extensions of the corolla in ray florets. These structures generally exhibit simple anatomy, often unvascularized in foliar types, with dimensions varying widely: 0.1-5 mm in , , and lycophytes, and up to 50 mm or more in . The tissue composition varies by group but in foliar ligules is predominantly , featuring two layers of uniseriate cells enclosing a thin mesophyll layer of cells, which may include limited chlorenchyma. The abaxial is often cutinized, while the adaxial side is less differentiated, with mesophyll 2-5 cells thick, lacking extensive intercellular spaces, stomata, or trichomes in membranous forms; sclerenchyma may provide in thicker variants, and vascular traces are rare.

Structural Variations Across Groups

In , ligules typically exhibit a membranous form that is truncate or rounded at the apex, often classified into types such as eciliate membrane, ciliolate membrane, ciliate membrane, or a fringe of hairs, with the majority being homoligulate on the ventral side. These structures are generally delicate and translucent, varying in size from very short (less than 0.5 mm) to very long (over 5 mm), and may include microscopic features like vascular strands or marginal cilia in certain subtypes. Developmentally, the ligule originates from the leaf primordium via a specialized boundary domain known as the preligule band in the adaxial at the presumptive sheath-blade junction, undergoing anticlinal then periclinal cell divisions to form the mature structure, regulated by genetic modules for precise patterning. In contrast, ligules in display greater diversity in form, frequently appearing fimbriate or fringed due to margins, with textures ranging from soft membranous to firm and toothed, as seen in genera like and Scleria where they are fused to the leaf blade base. Size variations are prominent, from minute projections under 1 mm to more prominent structures up to several millimeters, often accompanied by microscopic trichomes or a fused contraligule—a triangular or deltoid outgrowth on the abaxial side—distinguishing them from the open-sheath ligules of . Ligules in , particularly in ray or ligulate florets, adopt a distinctly petaloid form, consisting of a strap-shaped corolla limb that is flattened and elongated, typically with five minute apical teeth and a tubular base, contrasting sharply with the foliar appendages in monocots. These ligules vary in length from short (under 5 mm) to long (over 20 mm) and feature a colorful, textured with secretory cells or glands, emphasizing their modified floral rather than vegetative morphology. Within , such as in species, ligules manifest as small, scale-like tonguelike outgrowths on the adaxial surface near the base, structured into a glossopodium of minute basal cells and an elongated body with distinct base, neck, and apex regions featuring varying thicknesses. Morphological variations include campanulate, linguiform, elliptic, fan-shaped, or rectangular forms, with sizes ranging from 98 μm to 349 μm, and microscopic details like isodiametric cells and protoplasmic density, setting them apart as unique microphyll appendages unlike those in angiosperms.

Functions and Adaptations

Primary Functions

The ligule primarily serves a protective function at the junction between the sheath and blade, acting as a barrier to minimize loss, deter pathogens, and exclude and . In grasses (), the membranous ligule forms a tight seal against the culm, with its thick, unbroken on the abaxial providing a watertight barrier that prevents ingress of , dust, and harmful spores, thereby reducing the risk of fungal infections. Hairs or trichomes on the ligule surface further enhance this by deterring penetration and contributing to a hydrophobic character that repels moisture. Similar protective roles are observed in lycophytes like , where the ligule helps retain moisture around developing primordia and sporangia, shielding them from . In addition to protection, the ligule plays a key developmental role by facilitating orderly emergence and maintaining structural integrity during growth. It guides the unfolding of young leaves by providing a lubricated interface—potentially through secretory products—that allows smooth exsertion of the from the sheath without tearing the surrounding tissues. This is particularly evident in grasses, where the ligule's concave shape and close appression to the culm reduce constrictive forces at the sheath- junction, supporting shoot development. In lycophytes, the ligule's glandular nature secretes or absorbs water to hydrate emerging lycophylls, ensuring proper expansion. These functions underscore the ligule's conserved role in promoting healthy ontogeny across diverse plant groups. Hydrophobic properties, arising from cuticular waxes and surface microstructures, are a critical aspect enabling these primary functions, particularly in preventing environmental stresses at the vulnerable junction. In some ligules, such as those in grasses, the abaxial cuticle's impermeability not only seals against but also inhibits adhesion, while in floral ligules of , ultraviolet-reflective patterns on the strap-like extensions reduce from the corolla, aiding . Overall, these mechanisms highlight the ligule's adaptive versatility in safeguarding plant tissues during both protection and development.

Ecological and Physiological Roles

Ligules in various plant groups exhibit specialized physiological roles that enhance survival under environmental stresses. In grasses (), the membranous ligule functions as a barrier to prevent , , and pathogens from entering the leaf sheath, thereby reducing the risk of rot and in humid or dusty conditions; this protective mechanism is complemented by its secretory activity, where ultrastructural analyses reveal glandular tissues that may release substances aiding in local defense or . In lycophytes such as (Lycopodiopsida), which often inhabit arid or semi-arid environments, the ligule serves a key physiological role in moisture retention and absorption, secreting or facilitating water uptake to maintain hydration of young leaves during dry spells. Ecologically, ligules contribute to interactions within plant communities and with biotic agents. In , the elongated floral ligules of ray florets act as visual attractants for pollinators, increasing visitation rates and in open, competitive habitats like grasslands and meadows; color patterns and UV reflectance on these ligules further enhance pollinator guidance toward disk florets. While primary functions emphasize structural protection, these roles highlight ligules' integration into broader ecological adaptations.

Occurrence in Plant Groups

In and

In the family, commonly known as grasses, the ligule is a characteristic membranous outgrowth arising from the inner surface of the leaf sheath at its junction with the leaf blade. These ligules are typically thin and translucent, often featuring ciliolate (fringed with short hairs) margins, which contribute to their variability across species. For instance, in wheat (Triticum aestivum), the ligule is a short, truncate membranous flap, approximately 1–2 mm long, that encircles the culm where the blade diverges from the sheath. In contrast, many bamboo species exhibit pointed or acuminate ligules, which are thin membranes at the apex of the leaf sheath, aiding in species-level identification within this diverse subfamily. In the family, or sedges, ligules are frequently reduced, absent, or poorly developed compared to those in grasses, reflecting the family's distinct leaf architecture where sheaths are generally closed and blades arise directly from the sheath summit. When present, sedge ligules appear as a small fringed line of hairs or a bifid (two-cleft) membranous structure fused to the base of the blade, rather than a free-standing ; some genera also feature contraligules, which are analogous abaxial membranous or structures at the sheath-blade junction. This contrasts with the more prominent, independent membranous ligules typical of , as sedge ligules, if developed, are often subtle and integrated into the sheath-blade transition. The morphology and presence of ligules serve as critical diagnostic traits in taxonomy for distinguishing from , two major monocot families often confused due to superficial similarities in their habit. In grasses, the consistent presence of a well-defined ligule—along with open sheaths and alternate leaves—contrasts with the variable or absent ligules in sedges, which typically feature closed sheaths and three-ranked leaves, facilitating reliable field identification. For example, (reed canary grass) in displays a prominent, membranous ligule 4–11 mm long, often folded and lacking a hairy fringe, which exemplifies how ligule characteristics aid in separating grass species from sedge relatives in ecological surveys and floristic keys.

In Asteraceae

In the family, commonly known as the daisy or sunflower family, the ligule is a distinctive floral structure found in the ray florets of the composite flower head, or capitulum. Unlike the vegetative ligules in other groups, these floral ligules consist of a strap-shaped corolla limb formed by the fusion of five s, which create a short tubular base that expands asymmetrically into the elongated ligule. The apex of the ligule is typically three-lobed, with minute teeth representing the fused petal tips, contributing to the zygomorphic of the ray floret. These ligules are often brightly colored in shades of yellow, white, pink, or purple, enhancing the visual appeal of the to attract pollinators such as . Their length varies widely across , typically ranging from 1 to 50 mm, allowing for diverse display sizes in the flower head. For instance, in sunflowers (Helianthus annuus), the prominent yellow ligules measure 25 mm or more, surrounding the central disc florets to form a large, showy capitulum up to 30 cm across. In contrast, ligules can be reduced or entirely absent in some genera, leading to discoid heads composed solely of tubular disc florets. Thistles in the genus , such as bull thistle (C. vulgare), exemplify this variation, lacking ray florets and thus ligules, which results in compact, spherical inflorescences relying on the color and structure of the disc florets for attraction. The presence and arrangement of ligules around the disc thus play a crucial role in the overall architecture of the capitulum, mimicking a single elaborate flower to optimize efficiency.

In Lycopodiopsida

In , also known as lycophytes or clubmosses and allies, ligules are small, flap-like or scale-like outgrowths primarily found on the adaxial (upper) surface near the base of microphylls, the simple leaves characteristic of this group./07:_Ferns_and_lycophytes/7.02:_Lycophytes) These structures are absent in the order Lycopodiales, such as in the genus , where leaves lack any such outgrowth, distinguishing them from other lycophyte lineages. In contrast, ligules are a defining feature of the heterosporous orders Selaginellales and Isoetales, serving as a key anatomical trait in the classification of fern allies. Within Selaginellales, represented by the genus Selaginella, ligules are tongue-shaped or variably shaped membranous appendages embedded in a pit-like structure (ligular pit) at the leaf base. Anatomically, the ligule consists of a basal glossopodium—a small pad of two rows of minute cells—and an elongated body differentiated into three regions: a thin-walled base, a thickened-cell neck for structural support, and a thin-walled apex that may be lobed, rounded, or truncate. The body exhibits five primary shapes across species—campanulate, linguiform (tongue-like), elliptic, fan-shaped, and rectangular—with the ligule size correlating to the supporting leaf's dimensions. In Selaginella kraussiana, mature ligules feature three zones of cells, with the central zone showing advanced differentiation including extensive endoplasmic reticulum, Golgi apparatus, and agranal plastids, though the structure lacks vascular tissue. Ligules in are particularly prominent in desiccation-tolerant species like S. lepidophylla, the native to arid regions, where they contribute to moisture retention around developing leaves and sporangia during hydration cycles. Proposed roles include of young tissues and possible of water or , though their exact function remains enigmatic and not linked to large-scale mucilage production. In Isoetales, such as the quillworts (Isoetes), ligules are minute, triangular to cordiform membranous flaps at the base of the upper leaf surface, often positioned above the sporangium and below a flap-like velum. These ligules develop precociously on young leaves and exhibit ultrastructural zonation, with basal regions rich in secretory cells containing mucilage precursors, aiding in localized hydration. Like those in Selaginella, Isoetes ligules are non-vascular and play a role in maintaining humidity for gametophyte development within enclosed sporangia.

Evolutionary and Comparative Aspects

Evolutionary Origins

The ligule first emerged in the lineage during the period, representing an early innovation in leaf morphology. Fossil evidence from Leclercqia complexa, a Middle Devonian lycopod, documents the earliest known occurrence of a ligule as a small, flap-like outgrowth on the adaxial surface of microphylls, suggesting its role in stabilizing attachment or facilitating water relations in humid, swampy environments. This structure is considered an evolutionary novelty unique to heterosporous lycophytes, such as and , and likely homologous to marginal extensions of primitive tissue in early . Ligule-like structures persisted and diversified in clubmoss fossils, including arborescent lycopsids from the Lower Price Formation, where they appear as distinct projections amid scale-like leaves, indicating continuity through the coal swamp flora. In angiosperms, ligules evolved independently from those in lycophytes, arising during the period as part of divergent and floral adaptations. Within , the ligule originated in the common ancestor of the family around 100 million years ago, as a flap at the sheath-blade junction, homologous to the distal margin of the sheath in early monocot leaves. Ancestral forms were homoligulate and , with subsequent evolution toward membranous types in major clades like the BOP (Bambusoideae, Oryzoideae, ), reflecting parallel developments tied to habitat shifts; similar ligules evolved independently in and within . This innovation contributed to the of grasses in expanding post- grasslands, enhancing protection and photosynthetic efficiency during the . Similarly, in , ligules refer to the strap-shaped corollas of ray florets within the composite (capitulum), which evolved independently in the , coinciding with the family's origin approximately 83 million years ago. These ligulate structures derive from elaborations of ancestral tubular corollas in the proto-Asterales, promoting visual attractants for pollinators through bilateral symmetry. analyses place early diversification of lineages, including those with capitula featuring prominent ligules, in the early , around 60–50 million years ago, aligning with the radiation of bee-pollinated flora.

Comparative Anatomy

Ligules across plant groups, including , , and , exhibit anatomical variations that underscore both shared developmental origins and distinct evolutionary trajectories. In (grasses), ligules arise as epidermal outgrowths at the junction of the leaf sheath and blade, forming a membranous or structure derived from the inner sheath . Similarly, in (lycophytes such as ), ligules develop as multicellular epidermal on the adaxial surface of microphylls, originating from leaf primordia tissue. These shared epidermal origins suggest a common developmental pathway for appendage formation in early vascular , though the structures are not strictly homologous due to divergent phylogenetic positions. Despite these epidermal parallels, ligules demonstrate in their protective roles, adapting independently to shield bases from environmental stresses in disparate lineages. For instance, the ciliate or membranous ligules in parallel the flap-like ligules in , both serving as barriers without implying direct ancestry. In , ligules take a floral form as strap-shaped extensions of ray floret corollas, lacking the vegetative epidermal base seen in the other groups and instead deriving from petaloid tissue. This convergence highlights how similar anatomical solutions—thin, outgrowth-like structures—arose polyphyletically to address analogous selective pressures. Key anatomical differences further distinguish ligules among these groups, particularly in vascularization and cellular composition. ligules, as in species, possess a median positioned near the glossopodium base, providing limited vascular continuity with the microphyll's and supporting structural integrity in these small-leaved . In contrast, grass ligules in are typically avascular, lacking veins or vascular traces and consisting solely of epidermal and subepidermal layers without internal conduction tissue. Cellularly, ligules feature thin-walled, isodiametric cells with variable prickle hair densities, while ligules show a stratified body with a basal region of thin-walled cells, a thickened neck, and an apical zone of vacuolate cells, revealing greater complexity in tissue differentiation. Microscopy and phylogenetic analyses have been instrumental in elucidating these anatomical disparities. Scanning electron microscopy (SEM) reveals surface details such as unicellular hairs and membrane textures in ligules, enabling comparisons of cellular ornamentation across species like , where hair density varies from sparse to dense without altering core epidermal layering. In , light and electron microscopy highlight the multicellular glossopodium and ligule body divisions, contrasting the simpler, veinless in grasses. Cladistic analyses, incorporating morphological and molecular , demonstrate the polyphyletic origins of ligules, with independent emergences in lycophytes and monocots like , supported by phylogenetic reconstructions showing reversals and parallel evolutions within subfamilies.

References

  1. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/ligule
  2. https://sweetgum.nybg.org/science/glossary/glossary-details/?irn=1752
  3. https://floranorthamerica.org/Asteraceae
  4. https://nph.onlinelibrary.wiley.com/doi/full/10.1046/j.1469-8137.2000.00618.x
  5. https://www.merriam-webster.com/dictionary/ligule
  6. https://link.springer.com/article/10.1007/BF01276611
  7. https://www.sciencedirect.com/science/article/pii/S036725302400029X
  8. https://www.britannica.com/plant/Asteraceae
  9. https://www.britannica.com/science/ligule
  10. https://forages.oregonstate.edu/regrowth/how-does-grass-grow/grass-structures
  11. https://doi.org/10.1007/s12229-022-09285-3
  12. https://ir.library.oregonstate.edu/downloads/fb494h245
  13. https://mtnhp.mt.gov/resources/botany/terminology
  14. http://w3.biosci.utexas.edu/prc/K12/Glos.html
  15. https://www.britannica.com/plant/Cyperaceae/Characteristic-morphological-features
  16. https://www.researchgate.net/publication/362922013_The_Ligule_in_Poaceae_a_Historical_and_Evolutionary_Review
  17. https://www.oed.com/dictionary/ligule_n
  18. https://www.dictionary.com/browse/ligula
  19. https://bugguide.net/node/view/111045
  20. https://bio.libretexts.org/Bookshelves/Botany/A_Photographic_Atlas_for_Botany_%28Morrow%29/13%253A_Leaves/13.01%253A_Leaf_Parts_and_Arrangement
  21. https://www.illinoiswildflowers.info/files/line_drawings.htm
  22. https://nph.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1469-8137.2000.00618.x
  23. https://www.jstor.org/stable/2432895
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC10629682/
  25. https://www.nature.com/articles/s41477-023-01405-0
  26. https://doi.org/10.1016/j.sajb.2023.04.011
  27. https://doi.org/10.1016/j.flora.2024.152476
  28. https://www.biologydiscussion.com/botany/pteridophyta/selaginella-habitat-features-and-reproduction/46084
  29. https://www.sciencedirect.com/science/article/abs/pii/S0367253018305759
  30. https://ri.conicet.gov.ar/bitstream/handle/11336/257146/CONICET_Digital_Nro.02ba3f45-c98c-4c8a-b3fa-9b5848663c8a_B.pdf?sequence=2
  31. https://elifesciences.org/articles/72072
  32. https://pmc.ncbi.nlm.nih.gov/articles/PMC6026493/
  33. https://floranorthamerica.org/Poaceae
  34. https://www.fao.org/4/y4011e/y4011e05.htm
  35. http://bamboo-identification.co.uk/html/leaves.html
  36. https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=115
  37. https://www.researchgate.net/publication/369997808_Ligule_and_contraligule_in_Cyperaceae_A_systematic_review
  38. https://link.springer.com/chapter/10.1007/978-3-662-03531-3_15
  39. https://ezcurralab.ucr.edu/sites/default/files/2020-05/13_poaceae.pdf
  40. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30000197-2/general-information
  41. https://gobotany.nativeplanttrust.org/species/phalaris/arundinacea/
  42. https://mgnv.org/plants/glossary/capitulum-disk-disk-floret-floret-ligule-ray-floret/
  43. https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19590
  44. https://passel2.unl.edu/view/lesson/518875935c4c/1
  45. https://scholarworks.umt.edu/cgi/viewcontent.cgi?article=8439&context=etd
  46. https://openprairie.sdstate.edu/nativeplant/71/
  47. https://www.illinoiswildflowers.info/weeds/plants/bull_thistle.htm
  48. https://ucmp.berkeley.edu/IB181/VPL/Lyco/Lyco1.html
  49. https://onlinelibrary.wiley.com/doi/10.1111/cla.12136
  50. http://www.vpscience.org/materials/SELAGINELLA.pdf
  51. https://academic.oup.com/aob/article-abstract/49/5/569/151063
  52. https://www.uvm.edu/~cparis/PBIO108/PBIO108Labs/PBIO108_Lab_3_Selaginella_and_Isoetes.pdf
  53. https://www.jstor.org/stable/2442402
  54. https://www.sciencedirect.com/science/article/abs/pii/S036725302400029X
  55. https://www.sciencedirect.com/science/article/abs/pii/S0166516209002018
  56. https://www.sciencedirect.com/science/article/pii/S1674205222000156
  57. https://link.springer.com/article/10.1007/s12229-022-09285-3
  58. https://pmc.ncbi.nlm.nih.gov/articles/PMC6628808/
  59. https://abcbot.pl/pdf/48_2/83-88.pdf
Add your contribution
Related Hubs
User Avatar
No comments yet.