Thelypteris erubescens

Thelypteris erubescens (Wall. ex Hook.) Ching, Bull. Fan Mem. Inst. Biol., Bot. 6: 293 (1936) as per POWO;

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Glaphyropteridopsis erubescens (Wall. ex Hook.) Ching, Acta Phytotax. Sin. 8(4): 320 1963. (syn: Aspidium erubescens (Wall. ex Hook.) Christ; Asplenium distans var. carieri Christ; Asplenium glanduliferum Wall.; Christella erubescens (Wall. ex Hook.) Lév.; Cyclosorus erubescens (Wall. ex Hook.) C. M. Kuo; Dryopteris braineoides (Bak.) C. Chr.; Dryopteris erubescens (Wall. ex Hook.) C. Chr.; Dryopteris reflexa Ching; Glaphyopteridopsis erubescens var. mollis (Hook.) Ching; Glaphyropteris erubescens (Wall. ex Hook.) Fée; Lastrea erubescens (Wall. ex Hook.) Copel.; Nephrodium braineoides (Bak.) Diels; Nephrodium erubescens (Wall. ex Hook.) Diels; Phegopteris erubescens (Wall. ex Hook.) J. Sm.; Polypodium braineoides Bak.; Polypodium erubescens Wall.; Thelypteris erubescens (Wall. ex Hook.) Ching);

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Himalaya to S. Japan and Philippines: Assam, China South-Central, China Southeast, East Himalaya, Japan, Laos, Myanmar, Nepal, Pakistan, Philippines, Taiwan, Tibet, Vietnam, West Himalaya as per POWO;
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id of a fern : Attachments (4).  4 posts by 2 authors.
Please help me in identifying this herbarium specimen…
dated 16th april 2013

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My guess is that it may well be Thelypteris erubescens. However identifying a fern from these particular photos as made available is full of problems as they do not adequately show what is needed to see.
1. The base of the lamina usually shows the most lobed or most developed part, not the apex or top part – so rather than four photos all showing the same features, we needed a photo to show the lamina-base. In this case, if it is T. erubescens, the lowest pinnae should be the longest and the lowest pair should be somewhat backward- or downward-deflexed. But we were not shown this crucial information – so can’t be sure the frond was not narrowed to its base as in many other species of Thelypteris.
2. The photos are not quite in focus and can’t be magnified to see details of the sori – and anyway the sori look over-mature, so one can’t see indusia. I guess there would have been a central double-row of rounded indusiate sori running up each pinnule (or pinna-lobe), but this is not shown.
3. Especially in Thelypteris, the venation is important to show – whether the veins are free (as they should be if it is T. erubescens), or whether opposite pairs anastomose beneath the sinus between pinnules. This cannot be seen so we needed one close-up photo showing the veins between a pair of pinnules.
4. We do need some sort of rough locality and ecology! T. erubescens is common in the Indo-Himalaya from Pakistan eastwards. One record also exists from South India, but the population needs confirming as the specimen also looks like T. tylodes and might be that instead. If this collection is from Karnataka, for example, it won’t be T. erubescens! We don’t even know for sure it is from India as no information was provided – at least let’s have the State and altitude. T. erubescens grows at upper-mid altitudes (say c. 6000-8000 ft.) and loves to be right beside streams in the rocks, where its huge fronds often arch over the water from their long, pale, robust stipes. The slightly similar T. tylodes though, likes more open banks and usually not right by water. We are just too lacking in information here, including from the photos.
Still I imagine it is probably T. erubescens – one confirmation is that in younger fronds (and especially visible on smaller sterile fronds, there are long, stiff, straight white hairs scattered along the underside of the pinna-costae or pinnule-costule, which are very useful to help distinguish it.
Let’s hope for photos showing the right thing and focussable or magnifiable next time!

Yes, you are correct.

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References:

POWO  Catalogue of Life  The Plant List Ver. 1.1  Encyclopedia of Life