science

Hymenophyllaceae

Hymenophyllaceae is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hymenophyllaceae rather than just read about it. In short: The Hymenophyllaceae, the filmy ferns and bristle ferns, are a family of two to nine genera (depending on classification system) and about 650 known species of ferns, with a subcosmopolitan distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfalls or springs. Fossil evidence shows that ferns of the family Hymenophyllaceae have existed since at least the…

Key takeaways

Hymenophyllaceae belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hymenophyllaceae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hymenophyllaceae from memory before moving on to harder problems.

Reference excerpt

The Hymenophyllaceae, the filmy ferns and bristle ferns, are a family of two to nine genera (depending on classification system) and about 650 known species of ferns, with a subcosmopolitan distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfalls or springs. Fossil evidence shows that ferns of the family Hymenophyllaceae have existed since at least the Upper Triassic.

Description They often appear as very dark green or even black clumps and may be mistaken for a robust moss or liverwort. The rhizome is usually thin and wiry and the fronds variously pinnate with a single strand ("nerve") of vascular tissue. As in most ferns, young fronds have circinate vernation. In most species, the frond, apart from the vascular tissue, is only a single cell thick, and they do not have any stomata. The cuticle is also greatly reduced or absent, leaving filmy ferns poikilohydric and very susceptible to desiccation where a reliable water supply is not present. The leaves occasionally bear hairs, but scales are generally not present. The sori are borne at the leaf margins at the end of the nerve. They are protected by conical, bivalvate, or tubular indusia. Within the sori, sporangia mature starting at the apex of the sorus and progressing to the base. They have a continuous, oblique annulus and release round, green trilete spores. The spores grow into thread- or ribbon-like gametophytes; in many species, the gametophyte has an extended, independent lifespan and can reproduce asexually by fragmenting or releasing gemmae. Individual plants may persist for many years.

Taxonomy In the molecular phylogenetic classification of Smith et al. in 2006, the Hymenophyllales, containing the single family Hymenophyllaceae, were placed in class Polypodiopsida sensu stricto (the leptosporangiate ferns). The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009) which placed all land plants in Equisetopsida, reclassified Smith's Polypodiopsida as subclass Polypodiidae and placed the Hymenophyllales there. The circumscription of the order and its families was not changed, and that circumscription and placement in Polypodiidae has subsequently been followed in the classifications of Christenhusz and Chase (2014) and PPG I (2016). The division of the family into genera was disputed, as of October 2019. Traditionally, only two genera of Hymenophyllaceae have been recognized: (1) Hymenophyllum with bivalved involucres, and (2) Trichomanes s.l. with tubular involucres. Subsequent proposals have created 34 genera (Copeland 1938), 6 genera (Morton 1968), 47 genera (Sermolli 1977), and 8 genera (Iwatsuki 1984). These classifications all had only limited regional acceptance. Recent molecular phylogenic studies do show two distinct monophyletic clades of fairly equal size, but they are only roughly aligned with the two traditional genera. For example, the traditional Trichomanes subtaxa Pleuromanes and Cardiomanes were shown to belong to the "hymenophylloid" clade. To reflect these recent discoveries Atsushi Ebihara and Kunio Iwatsuki, in 2006, revised the taxonomy of Hymenophyllaceae to place all species of the "hymenophylloid" clade in a single genus Hymenophyllum, and to place the eight clear "trichomanoid" subclades in eight corresponding genera. This subdivision was recognized by Smith et al. in 2006 and Christenhusz et al. in 2011, but Christenhusz and Chase, in 2014, reverted to combining the trichomanoid clades into Trichomanes. The PPG I classification of 2016 again recognizes the segregate genera (and treats the two clades as subfamilies, Hymenophylloideae and Trichomanoideae), although the segregate genera are not always accepted by contemporary floras; e.g., as of 2016, the Flora of New Zealand preferred to recognize Trichomanes s.l. due to the difficulty of morphologically distinguishing the segregate genera.

Genera The genera used in PPG I and the subgenera assigned by the system of Ebihara et al. are:

Hymenophylloideae (the "hymenophylloid" clade): Hymenophyllum Sm. 1793 – about 250 species subg. Hymenophyllum – about 100 species subg. Sphaerocionium (C.Presl) C.Chr. 1934 – about 70 species subg. Mecodium C.Presl ex Copel. 1937 – more than 35 species subg. Globosa (Prantl) Ebihara & K.Iwats. 2006 – about 25 species subg. Pleuromanes (C.Presl) Ebihara & K.Iwats. 2006 – 5 species subg. Myrmecostylum (C.Presl) Ebihara & K. Iwats. 2006 – at least 8 species subg. Hymenoglossum (C.Presl) R.M.Tryon & A.F.Tryon 1981 – at least 3 species subg. Fuciformia Ebihara & K.Iwats. 2006 – 2 species subg. Diploöphyllum (Bosch) Ebihara & K.Iwats. 2006 – 1 species subg. Cardiomanes (C. Presl) Ebihara & K.Iwats. 2006 – 1 species Trichomanoideae (the "trichomanoid" clade) (sometimes all included in a single broad genus Trichomanes with about 400 species): Didymoglossum Desv. 1827 – more than 30 species subg. Didymoglossum – more than 20 species subg. Microgonium (C.Presl) Ebihara & K.Iwats. 2006 – more than 10 species Crepidomanes (C.Presl) C.Presl 1849 – more than 30 species subg. Crepidomanes subg. Nesopteris (Copel.) Ebihara & K.Iwats. 2006 Polyphlebium Copel. 1938 – about 15 species Vandenboschia Copel. 1938 – more than 15 species subg. Vandenboschia – more than 15 species subg. Lacosteopsis (Prantl) Ebihara & K.Iwats. 2006 – at least 2 species Abrodictyum C.Presl 1843 – about 25 species subg. Abrodictyum – about 15 species subg. Pachychaetum (C.Presl) Ebihara & K.Iwats. 2006 – more than 10 species Trichomanes L. 1753 – more than 60 species subg. Afrotrichomanes Dubuisson & Ebihara 2021 subg. Davalliopsis (Bosch) Ebihara & K.Iwats. 2006 – at least 1 species subg. Feea (Bory) Hook. 1844 – more than 5 species subg. Lacostea (Bosch) C. Chr. 1906 – more than 4 species subg. Trichomanes – more than 30 species Cephalomanes C.Presl 1843 – about 4 species Callistopteris Copel. 1938 – about 5 species

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Hymenophyllaceae

Start with the simplest possible case. Write down what Hymenophyllaceae claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hymenophyllaceae before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hymenophyllaceae ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hymenophyllaceae

In research: Hymenophyllaceae appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hymenophyllaceae in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hymenophyllaceae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fern families, Hymenophyllales, so understanding it makes those chapters shorter.
In everyday life: Look for Hymenophyllaceae outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hymenophyllaceae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hymenophyllaceae means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hymenophyllaceae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hymenophyllaceae in simple terms?

Why does Hymenophyllaceae matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hymenophyllaceae?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hymenophyllaceae.