i am not sure but they could be slugs eggs or mealy bug eggs. welcome to GOY.someone else may come up with a better answer.

I think this is fungus the pots are peat and when they get damp this grows I have seen it on mine this is why I do not use them anymore.Although I think its harmless

it is fungal growth and I havent found it to do any harm in the past.

just wipe it of as and when .

Looks like slime mold spore bodies developing--quite harmless to the plants, the fungus is probably eating the peat.

Sorry, Tulsalady, but mealybug eggs are a good deal smaller, are always covered with a white wool, and are only laid on living plants:

http://hortipm.tamu.edu/pestprofiles/sucking/mealydawn/mealyegg.jpg

I agree with all the above comments. It is the start of the natural process of the loo roll inners decaying. I usually put the loo rolls very close together and that way little light gets to the sides. You may find a white fluffy mould grow on them and then small little toadstools appear, this is quite normal and will do the plant no harm. By keeping the loo rolls seperate as in the picture, you may find the cardboard decays quickly and the tubes may infact collapse. If it is possible, put them together to support each other.

Thank you very much for this intresting informations.
I will try to wipe those fungus and put loo roll closer.
I'm very happy to join this community. i'll keep you updated about my garden.
It's a little city garden that i share with my flat mate, it's very exciting.