More on mosses

Mosses have a complex and very interesting reproductive cycle: individual plant specimens are either male or female (although some have both male and female portions). The male plants produce gametes in the antheridium, which looks rather like a pepper-pot lid:

Antheridium on male moss plant

These male gametes swim towards the female gametes, which are held in the archegonium on the female plants. Fertilisation takes place and the offspring grows upwards, forming the seta ('stem') and eventually the spore-bearing capsule. This sporophyte looks like it is part of the original plant, but is actually parasitic on it, so when you see a spore capsule forming like the one below, it isn't one plant with green leaves and a spore capsule, it's the mother (leaves) and child (spore-producing sporophyte).

Emerging spore capsule on Polytrichum moss

Here's a shot of last year's capsules:

Old capsules of Polytrichum commune

The specimens I used for these photographs are Polytrichum commune, which is one of our larger mosses. The setae regularly reach over 8 cm. long, which makes them an ideal subject to use for initial moss studies, since everything is large enough to be seen with the naked eye.

The fact that the male gametes swim towards the females gives us one reason that mosses flourish in damp places.

The Stump

There's an old deciduous stump in Drumboe that demands that I photograph it on each visit. It's covered in lichens and mosses, with visits from occasional fungi, including the wonderful 'Jelly Tooth' that I might see there again soon. Here is a small (15cm.) fragment:

It's the kind of environment that draws you right into it. "You have to get down to its level", as a good friend told me (you know who you are).

I made another image, so that I can point out the various species:

1) and 4) Polytrichum commune - one of the 'Hair Cap' mosses.

2) Cladonia fimbriata - a lichen.

3) Pleurozium schreberi - a moss.

5) Cladonia portentosa - a 'Reindeer Lichen'.

6) A Birch seedling.

There will be more that I can't make out from the pictures.


Here's a close-up of the Cladonia portentosa:


Incidentally, this is a perfect example of lichens getting on with their work. The stump started off as clean dead wood and lichens (not Cladonias: they come later) colonised it, converting the wood into poor, thin, soil. The mosses need hardly any soil, so they come in after the lichens and then they, too die off and leave more organic material behind them. Eventually the soil is sufficient for a tree to take root above the old stump. I don't know how old the stump is (perhaps 20 years?), but the sequence of events is classic: Lichens are the pioneers, lower plants follow in and higher-order plants arrive last. Without lichens there is nothing. The same process takes place on rocks (and gravestones) but the process takes slightly longer.

Exotics in the bog

I'm always amazed by the complexity and beauty of Bog Asphodel. It just seems too exotic to be in a local bog.

The Common Spotted Orchids are very large and numerous this year. I found three on the lawn of our local Health Centre.

One of the most common mosses at the fringe of the bog: Polytrichum commune.


And at the very edge of the bog, my favourite flower: Slender St. John's Wort.

Moss life-cycle

I have been trying to decipher the life-cycle of mosses, and believe I now have it worked out. For so-called 'primitive plants', mosses have a complex life-cycle.

We'll start with the sexual generation, with male antheridia and female archegonia, which are usually - but not always - borne on separate plants. The following shot shows the cone-shaped antheridia of Polytrichum commune.


These produce the male gametes which swim (through water, hence the need for humidity around mosses) towards the female archegonia, which are tiny pockets on the stem of the female plant:
Fertilisation takes place, resulting in the sporophyte, or asexual spore-bearing generation, which grows as a parasite on the female shoot. So although the sporophyte - which consists of the seta (capsule-bearing 'stem') and the capsule (spore-bearing container) - appears to be part of the female plant, it is only 50% hers.

This shot shows the immature sporophytes of Polytrichum commune.


And these are the mature sporophytes with open capsules: