"Geoff Bryant" wrote in message
...
They're liverworts, primitive plants allied to mosses. The "octopus
suckers"
are the fruiting bodies that will release spores. Liverworts don't really
do
any damage but they can become very abundant and may make watering from
above rather difficult. A little touch of iron sulphate, just half a pinch
on the surface, will knock them back.


Thanks for the replies.

Where do I get iron sulphate? Gardening centre, or a chemists? I have
noticed liquid fertiliser kills ordinary moss in plant pots, would this do
the trick?

Bob