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HART'S-TONGUE THYME-MOSS

Plagiomnium undulatum

(Formerly: Mnium undulatum)
Mosses Family [Mniaceae]

Leaves:
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category
category8Mosses

31st July 2007, Silverdale, Lancashire. Photo: © RWD
Grows in basic or neutral soils, here on a limestone wall in a dark corner of a narrow path under trees. An unusual looking moss.


31st July 2007, Silverdale, Lancashire. Photo: © RWD
Several branches extend from a single origin in tufts.


31st July 2007, Silverdale, Lancashire. Photo: © RWD
The branches have alternate leaves which are so thin as to be translucent light-green.


31st July 2007, Silverdale, Lancashire. Photo: © RWD
The leaves are paper-thin and wavy with many small teeth near te pointed tip. Leaves join the stem directly and without stalks.


Not to be semantically confused with : Wild Thyme [a herb with similar name]

Easily mis-identified as : a Filmy-Fern

Many similarities to : other Thyme-mosses.

No relation to : Hart's-tongue Fern (Asplenium Scolopendrium) [a fern with similar name].

When your Author first espied this he correctly thought it was a moss, but when he looked at it on his computer screen and saw how translucent the leaves were, started looking elsewhere for a match. He then tentatively thought that it must be a Filmy-Fern, albeit one which he couldn't match to the only two species known in the UK. He then left it in the 'unknown' pile for several years. Only after submitting to an expert for examination did he realise he was correct in his first thinking, it is a moss. And fairly common at that. Found throughout the UK without a hectad missing in the distribution.

The difficulty lies in differentiating between it and another five species of Thyme-moss found in the UK, some of which look very similar. These are:

  • Many-fruited Thyme-moss (Plagiomnium affine) but that has shorter rounder leaves.
  • Woodsy Thyme-moss (Plagiomnium cuspidatum) but that has some strongly toothed leaves.
  • Tall Thyme-moss (Plagiomnium elatum) but this has longer shoots and grows in low-lying ground near flushes and streams.
  • Long-beaked Thyme-moss (Plagiomnium rostratum) but this has leaves that do not run down onto the stem.
  • Marsh Thyme-moss (Plagiomnium ellipticum).
There are other differences, some of which require the use of a hand-lens to see.

None of the Thyme-moss species are associated with tree trunks.

The capsules of this specimen occur in-frequently, but when they do materialise, are on long stalks which often emerge in a small grouping from the same point.


  Plagiomnium undulatum  ⇐ Global Aspect ⇒ Mniaceae  

HART'S-TONGUE THYME-MOSS

Plagiomnium undulatum

(Formerly: Mnium undulatum)
Mosses Family [Mniaceae]

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