Tar spot

It has been a bit of a bitty day today, with lots of little things done.
I went out for a while this afternoon, but just as I decided to go out, the weather took a turn for the worse and the sun disappeared and the clouds closed in ...not nice photography weather at all! 
Luckily I did find this pretty leaf made all the more interesting by the black 'tar spot' on it caused by the fungus Rhytisma acerinum.
Tar spot affects Acer species particularly  sycamore. and even though it's unsightly it has no long term effect on the tree other than causing the leaves to fall slightly early.
Once the affected leaves have fallen tiny fruiting bodies develop during the winter . These fruiting bodies then produce microscopic spores in April and May which are carried up on air currents to infect the newly-emerging leaves and start the cycle all over again.