Wednesday, 10 November 2010

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)


Emma Springfield said...

What a marvelous site you have. I have been having such an adventure looking through all your posts. Your pictures are so detailed and crisp and the descriptions have taught me a great deal.
Your site is the Nature Site of the Week at Nature Center Magazine.

Stuart said...

Emma, thank you for your kind words and for featuring the site on your magazine. Things are certainly slowing down in terms of insects and flowering plants, but mosses, lichens and liverworts are now at their best (and most visible). Keep looking in.