Moss Hand Sections

[mrsonchus]

Hi all, I've been practising with moss leaf and stem today, trying out the taking of hand sections cut along the edge of a slide placed over the leaf or stem to be cut.

Thought I'd share a few images, hope to do a few more tomorrow if I get the chance. These are all temporarily mounted in neat PVA glue and coverslip, imaged with my Orthoplan compound 'scope.

Here are top and bottom views of a leaf, almost identical except for the central 'nerve'...


The leaf has a long, finely-toothed 'hair' that's nearly as long as the leaf-blade!


Underside where hair leaves leaf-tip,


There's a mid-rib or 'nerve' as these thickened central strands are called in mosses. The above hair-tip is an extension of this nerve it seems.


The edges of the leaf are 'rolled under' from the base to about halfway up the blade,


Halfway up the edge 'flattens out',


The edge of the leaf looks pretty papillose, as do the blade (lamina) cells, at least in the upper regions of the leaf,


Towards the leaf base the cells become elongated and 'hyaline' (having some translucency),

and,



This moss also has rhizoids at the base of it's leaves, seen here around the base of a detached leaf as the brownish filaments,


In transverse-section the leaf is seen to have a central nerve with a degree of cellular differentiation, namely thickened cells 'around' the bottom of the nerve with top/central larger-bore water-conducting (maybe?) cells within this strengthened 'jacket or cylinder. The top edge of the nerve is pretty flat and level with the leaf blade, and looks papillose as do the leaf edge and blade....


The stem in TS doesn't appear to have a well defined central 'core' as seen in the leaf nerve, but these are just unstained hand sections, maybe closer inspection and staining would reveal a more definitive image..... There appear to be rhizoids or maybe 'paraphyllia' emerging along the surface of the stem also. The thickened epidermis and maybe even a cortex of sorts are evident, also chlorophyll seems to extend quite a way into the cortex, beyond the epidermis.


Closer-in the transition from thinner to thicker cell walls is seen from center to cortex to epidermis across the stem,


The cells at the center seem thin-walled and not really larger or noticeably adapted for water transport as in some mosses,


Finally a couple of gratuitous polarised images across the stem,


and,


Well, sorry to bombard with images, I just thought some of them were interesting and that I may as well share them. It's amazing to see just what may be discovered from a tiny piece of moss stem and a few attached leaves. Next time I must take the time to do a 'proper job' and include capsules if I can find some - it's a little early for mature capsules here in the U.K. A touch of staining would be nice too I think!

In fact, it's about time I made some permanent sections of moss features, hmm, I really would like to get some made.

Anyway, just a quick indulgence in my 'mossy playtime' of today....

John B.

[Rylander]

Hi John B.

You have found Great Hairy Screw-moss (Syntrichia ruralis subsp. ruralis)
It's a common moss that grows on calcareous substrates on walls, rocks and sandy grounds.

It's nice that you've started on mosses, I'm a bryologist, and it's nice stuff you've laid up around mosses.

Rylander

[mrsonchus]

Hi John B.

You have found Great Hairy Screw-moss (Syntrichia ruralis subsp. ruralis)
It's a common moss that grows on calcareous substrates on walls, rocks and sandy grounds.

It's nice that you've started on mosses, I'm a bryologist, and it's nice stuff you've laid up around mosses.

Rylander

Haha! Thanks Rylander - I suspected the .ruralis but wasn't sure a few days back... It's really, really handy to have you aboard for IDs as I'm very limited indeed in this area at present my friend.
I've a few mosses that have been in fixative for plenty of time, with capsules, that I think I may give a similar treatment together with the making of some permanent microtome-cut slides, stained too. I don't know quite why but I really do find mosses and their variety quite fascinating, almost up there with the higher plants.

Thanks for looking and the ID my friend.

John B.

[jimur]

I'm a nobody, but I certainly forgive and fully appreciate the bombardment. I can always be assured your post will benefit me. Thanks.

[Hobbyst46]

I've a few mosses that have been in fixative for plenty of time, with capsules, that I think I may give a similar treatment together with the making of some

Hi John B.
As always, beautifully informative images!
Which fixative is it? does it preserve the green color of the moss?

[Rylander]

Hi John

Lots of great pictures, when I answer last, there was only one picture.
You only find paraphyllia of the pleurocarpous mosses, Screw-moss is acrocarpous moss, so it's rhizoids.
Leaves does not have a central strand, but they have stereids or stereid cells in the costa of the leaves of some mosses.

Rylander

[mrsonchus]

Thanks Jimur, pleased you like them.

Hi Hobby' - no the fixative clears the green - I use FAA pre-processing for paraffin wax sectioning, I've been moving some mosses from the FAA after a couple of days into approx 70% isopropanol to 'see how they fare' but again, the green is lost - I stain the microtome sections of course.

Thanks Rylander - would the larger thin-walled cells above the stereids be hydroids, although not joined as in a vessel presumably?

Thanks for looking chaps, John B.

[Rylander]

Hi John

You only find hydroids in the stem of Haircap mosses (Polytrichum/Polytrichastrum) and only a few other mosses , and in some liverworts, or in the seta of some mosses.

Rylander

[mrsonchus]

Thanks Rylander, what would the larger cells above the stereids be called?

Do they have a particular name?

John B.

[Rylander]

Hi John

The big cells in the costa or midrib is call guide cells.
I looked at Flora of North America vol. 27, and I found, that you can find, hydroids in leaves. All this and much more about morphology and anatomy can be found in Chapter 1, in the book. See below

http://flora.huh.harvard.edu/FloraData/ ... apter1.pdf

Rylander

[PNWmossnerd]

Beautiful leaf preparations!

The guide cells (also called deuters) are actually sugar conducting cells in the leaves. Sugar-conducting cells (leptoids) are common in moss leaves, but are only found in the stems of Polytrichaceae. Hydroids and leptoids are found in the seta of many mosses. Hydroids are also found in a variety of moss stems. Leaf traces, where the conducting tissues of the leaves penetrate the cortex of the stem are also known in several moss lineages. Conducting tissues in mosses are most complex in members of the family Polytrichaceae.

When you find hydroids in leaves, they are often quite small and arranged in a single band in the costa. They can only be seen at high (>200x) magnification. However, no hydroids are present in the leaves of Syntrichia.

I apologize for not having posted a guide to how I approach moss ID yet. I've been overwhelmed with school work as the term is coming to a close. I will probably get around to making that post early next year.

[mrsonchus]

Ah, so would it be correct to call those cells (in the leaf costa within the stereid 'band') leptoids as a kind of guide cell?

The little sample containing the Syntrichia.ruralis subsp ruralis has also a very similar moss, maybe a different subspecies?
The leaf apex is more tapered to the excurrent hair and the recurved margins run the whole length of the leaf.

Here are the two for comparison,any thoughts?

Here is the Syntrichia.ruralis subsp ruralis leaf,

ws_moss leaf and stem hand sections (20).jpg (42.98 KiB) Viewed 6382 times

Here's the very similar leaf, with a rather more tapered apex.
Similarities include strongly papillose lamina and the extent of the hyaline cells is roughly 40% from the leaf base.
This leaf appears to have a completely recurved leaf margin whereas the subsp ruralis seems to be recurved only up to about 60% from the base....

ws_19_12_18_305_stitch.jpg (27.03 KiB) Viewed 6382 times

ws_19_12_18_307_stitch.jpg (24.21 KiB) Viewed 6382 times

Any thoughts on these two compared? I'll try to get some better images tomorrow chaps....

John B.

[Rylander]

Hi John

It's look like, you have found the other subsp. Sand-hill Screw-moss (Syntrichia ruralis subsp. ruraliformis)

It's grows on sandy places or on concrete standings and corrugated asbestos roofs.

Rylander