biology

Jamesonia

Jamesonia is a biology 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 Jamesonia rather than just read about it. In short: Jamesonia is a genus of ferns in the subfamily Pteridoideae of the family Pteridaceae. It now includes the formerly separate genus Eriosorus.

Key takeaways

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

Reference excerpt

Jamesonia is a genus of ferns in the subfamily Pteridoideae of the family Pteridaceae. It now includes the formerly separate genus Eriosorus.

Description Species of Jamesonia are terrestrial or grow on rocks. They vary considerably in their detailed morphology. The rhizomes are short, dark brown, and creeping, with a more or less dense covering of hairs and bristles. The fertile and infertile fronds are similar. Species show one of two different frond morphologies, related to habitat. These were formerly used to distinguish Jamesonia and Eriosorus, but do not correspond to the evolutionary history of the species. Species with "Jamesonia-type" morphology have many fronds with short, often leathery pinnae, and are associated with exposed habitats. Species with "Eriosorus-type" morphology have fewer fronds with longer, thinner pinnae, and are associated with more sheltered areas including cloud forests. The stalks (petioles and rachises) of the frond are dark brown and usually grooved on the upper (adaxial) surface. The sori occur along the veins of the segments of the fronds or are sometimes spread more widely on the lower (abaxial) surface of the frond.

Taxonomy The genus Jamesonia was first described by William Jackson Hooker and Robert Kaye Greville in 1830, initially with one species, Jamesonia pulchra. The genus name of Jamesonia was in honour of William Jameson (1796–1873), who was a Scottish-Ecuadorian botanist. The genus Eriosorus, proposed by Antoine Fée in 1852, was recognized as closely related, both genera being placed in the taenitidoid group of the subfamily Pteridoideae. A molecular phylogenetic study in 2004 showed that neither genus was monophyletic on its own, but that together they formed a clade. Subsequent classifications have treated the two as a single genus, Jamesonia. A further study in 2015 showed that the genus Nephopteris with the sole species N. maxonii belonged in the same clade. It is now also included in Jamesonia.

Phylogeny Within the subfamily Pteridoideae, Jamesonia forms a clade with five other genera, the so-called "JAPSTT" clade, which is one of four major clades within the subfamily Pteridoideae identified in a 2017 study.

Other species:

References

Bibliography

Pichi-Sermolli, Rodolfo E. G. (1977). "Fragmenta Pteridologiae—VI". Webbia. 31 (1): 242. Bibcode:1977Webbi..31..237P. doi:10.1080/00837792.1977.10670073. ISSN 0083-7792. Schuettpelz, Eric; Schneider, Harald; Huiet, Layne; Windham, Michael D.; Pryer, Kathleen M. (2007). "A molecular phylogeny of the fern family Pteridaceae: Assessing overall relationships and the affinities of previously unsampled genera" (PDF). Molecular Phylogenetics and Evolution. 44 (3): 1172–1185. Bibcode:2007MolPE..44.1172S. doi:10.1016/j.ympev.2007.04.011. ISSN 1055-7903. PMID 17570688. Archived from the original (PDF) on 2008-08-20. Tryon, Alice F. (1962). "A monograph of the fern genus Jamesonia". Contributions from the Gray Herbarium of Harvard University. 191: 109–197. doi:10.5962/p.336405. JSTOR 41764668. Tryon, Alice F. (1970). "A monograph of the fern genus Eriosorus". Contributions from the Gray Herbarium of Harvard University. 200 (200): 54–174. doi:10.5962/p.336423. JSTOR 41764694.

Illustrations

Worked examples

Example 1 — a first encounter with Jamesonia

Start with the simplest possible case. Write down what Jamesonia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Jamesonia 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 Jamesonia 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 Jamesonia

In research: Jamesonia appears in biology 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 Jamesonia 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: Jamesonia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fern genera, Ferns of Brazil, Ferns of Mexico, so understanding it makes those chapters shorter.
In everyday life: Look for Jamesonia 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 Jamesonia in 20 minutes

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

Frequently asked questions

What is Jamesonia in simple terms?

Jamesonia is a genus of ferns in the subfamily Pteridoideae of the family Pteridaceae. It now includes the formerly separate genus Eriosorus.

Why does Jamesonia matter?

Because it connects several biology 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 Jamesonia?

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 Jamesonia.