science

Blechnaceae

Blechnaceae 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 Blechnaceae rather than just read about it. In short: Blechnaceae is a family of ferns in the order Polypodiales, with a cosmopolitan distribution. Its status as a family and the number of genera included have both varied considerably.

Key takeaways

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

Reference excerpt

Blechnaceae is a family of ferns in the order Polypodiales, with a cosmopolitan distribution. Its status as a family and the number of genera included have both varied considerably. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the family has 24 genera, and excludes genera placed in the separate family Onocleaceae. The family is divided into three subfamilies, including Blechnoideae s.s. Alternatively, the entire family may be treated as the subfamily Blechnoideae s.l. of a very broadly defined family Aspleniaceae, and include genera others place in Onocleaceae.

Description Most are ground dwelling, some are climbers, such as Stenochlaena. A characteristic feature of many species is that the young opening fronds are usually tinged with red.

Taxonomy The family was created by Newman in 1844. In 2014, Christenhusz and Chase submerged it as subfamily Blechnoideae within the family Aspleniaceae and included Onocleaceae in it. The PPG I classification of 2016 restored it to family status. Blechnaceae is a member of the eupolypods II clade (now the suborder Aspleniineae), in the order Polypodiales. It is related to other families in the clade as in the following cladogram:

Subdivisions The number of genera accepted within Blechnaceae (or Blechnoideae when treated as a subfamily) has varied between authors. Christenhusz and Chase (2014), treating the group as a subfamily, describe the situation as follows: "Blechnoideae comprise three major clades, one corresponding to Onoclea sensu lato, a second corresponding to Woodwardia, sister to all other species that can be treated as the single genus Blechnum. However, the subclade sister to the rest of Blechnum sensu lato contains the vining taxa Stenochlaena, Salpichlaena J.Sm. and a few non-vining Blechnum species with long-creeping rhizomes, which may have to be accepted at the generic level pending further studies. Brainea, Doodia, Pteridoblechnum and Sadleria belong to Blechnum sensu lato." Perrie et al. (2014) retained the family rank and excluded Onoclea as a separate family, Onocleaceae, sister to Blechnaceae. They identified three major clades within the remaining Blechnaceae, which they labelled Woodwardia, super-Stenochlaena and super-Blechnum, with the latter two as sister groups. They did not consider Blechnum as monophyletic and recommended revision of intergeneric boundaries, resulting in seven genera. Gasper et al. (2016), independently of Christenhusz and Chase, examined the deeper relationships of the Blechnaceae, retaining its family status and excluding Onocleaceae, and allocated the three major clades of Perrie et al. (2014) to subfamilies: Woodwardioideae, Stenochlaenoideae and Blechnoideae. Their approach to the polyphyletic nature of Blechnum was to create a series of monophyletic segregate genera, resulting in 24 genera in total. The relationship between the three subfamilies was found to be as follows:

The approximate relationship between some of the taxa used in the classifications of Christenhusz and Chase (2014) and PPG I (2016) is shown in the table below.

Subfamilies and genera

In 2016, the Pteridophyte Phylogeny Group followed Gasper et al. (2016) in accepting 24 genera, grouped into three subfamilies with approximately 265 species, most of which are placed in the subfamily Blechnoideae. Subfamily Woodwardioideae Gasper, V.A.O.Dittrich & Salino

Anchistea C.Presl Lorinseria C.Presl Woodwardia Sm. Subfamily Stenochlaenoideae (Ching) J.P.Roux

Salpichlaena J.Sm. Stenochlaena J.Sm. Telmatoblechnum Perrie, D.J.Ohlsen & Brownsey Subfamily Blechnoideae Gasper, V.A.O.Dittrich & Salino

Austroblechnum Gasper & V.A.O.Dittrich Blechnidium T.Moore Blechnopsis C.Presl Blechnum L. Brainea J.Sm. Cleistoblechnum Gasper & Salino Cranfillia Gasper & V.A.O.Dittrich Diploblechnum Hayata Doodia R.Br. Icarus Gasper & Salino Lomaria Willd. Lomaridium C.Presl Lomariocycas (J.Sm.) Gasper & A.R.Sm. Neoblechnum Gasper & V.A.O.Dittrich ×Oceanidoodia Liu, Schuettp. & H. Schneid. Oceaniopteris Gasper & Salino Parablechnum C.Presl Sadleria Kaulf. Struthiopteris Scop. Subfamily incertae sedis

†Trawetsia Smith et al Ypresian, Princeton Chert

References

Bibliography

External links Germplasm Resources Information Network: Blechnaceae

Illustrations

Worked examples

Example 1 — a first encounter with Blechnaceae

Start with the simplest possible case. Write down what Blechnaceae 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 Blechnaceae 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 Blechnaceae 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 Blechnaceae

In research: Blechnaceae 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 Blechnaceae 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: Blechnaceae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Blechnaceae, Fern families, Taxa named by Edward Newman, so understanding it makes those chapters shorter.
In everyday life: Look for Blechnaceae 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 Blechnaceae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Blechnaceae 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 Blechnaceae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Blechnaceae in simple terms?

Blechnaceae is a family of ferns in the order Polypodiales, with a cosmopolitan distribution. Its status as a family and the number of genera included have both varied considerably.

Why does Blechnaceae 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 Blechnaceae?

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 Blechnaceae.