Small but beautiful

As I mentioned the other day, we're moving into a good time to have a look at mosses. They tend to start making their spore capsules around now and they're often very attractive whilst the capsules develop and before they mature and dry off.

Polytrichum urnigerum

Capsules of Polytrichum urnigerum

Although they are considered to be some of our most primitive plants (spores vs. flowers, pollen and seeds), the life-cycle of mosses is rather complex, and it took me a while to work it all out.

There are two generations in the reproductive life-cycle: a vegetative stage (the green plants you see) and a dependent stage (the spore-bearing capsule and its associated stem [seta]). Spores are produced in the capsule and are dispersed by air or water (or, indeed, insects) and these each result in a male or female plant. Male plants produce gametes, which swim to fertilise the female egg. This fertilised egg develops into the seta and spore capsule, which are then parasitic on the female plant (capsules and setae have no chlorophyll, and therefore need to absorb food from the female parent). So each capsule-bearing 'plant' is actually two generations: the mother (with leaves) and the child (the capsule and seta). 

Setae of Ceratodon purpureus

All parts of a moss can be truly beautiful if looked at closely, but you really do have to 'get down to their level' both physically and metaphorically to appreciate just how beautiful they can be.

Mosses can be quite tricky to identify at first, with most needing microscopic analysis of leaves and some requiring examination of capsules. I have found, however, that once the initial identification has been performed, most specimens are readily identifiable in situ.

Mosses often grow in similar habitats to our other 'primitive' plants - liverworts and ferns - and also lichens.

Lichens are usually thought of as the flattish marks on walls and trees, but some of them appear to be quite leafy, as in the Peltigera family of Dog Lichens:

Fruit bodies of Peltigera hymenina

In common with all lichens, Peltigera are an association of a fungus and its trapped alga(e). The fungus provides the physical structure and the alga provides nutrients from sunlight. The orange fruitbodies shown above are purely fungal, and produce fungal spores in the same way as an independent fungus does.

(I'm just getting to grips with the new formatting tools)

More small things

Up in the deforested heath there is a slab of rock about 1m. across. This slab is a continual source of mosses, and I like to watch it at this time of year. This shot shows two of those mosses: in the foreground we have the hair-tipped leaves of Racomitrium lanuginosum, and the species with the elegant ruby-tipped capsules is Ceratodon purpureus.

This is how the Racomitrium looks in a habit shot. Specimen about 5 cm across.

Also on the rock is one of the smaller Polytrichums, Polytrichum juniperinum. These are male specimens, with the antheridia at the centre.

This green rosette might be a bit confusing at first, but once you get your eye in, it shouts 'liverwort'. Specimen about 6 cm. across.

Close-up examination reveals two rows of complex leaves, each doubled back on itself. This is diagnostic liverwort structure, and it turns out to be the very common Diplophyllum albicans. Main shoot about 12mm long.

There are also a few lichens in the area, on an old tree stump. This is Cladonia polydactyla, with tiny red fruitbodies. To the right you can see the Donegal speciality: Cladonia monodactyla (just joking).



And this is also a lichen, believe it or not. Peltigera membranacea, or Rabbit-paw lichen, growing through grass. Specimen about 30 cm. across.