But what is it !

Jim started the big prune of the row of Hydrangeas at the fron of the house and I did a bit of weeding out there. I went to pull some weeds from the far end of the drive which isn't used at all and found the whole area that had got mossy, was covered in these strange balls, some black and some as above.  No idea what they are -  I thought at first it was Rabbit poo, but then had a closer look  - any ideas ?
Thanks to Gaynor I now know it is Nostoc !
"Gelatinous balls seen on the bottom of lakes, especially in clear lakes where light reaches the bottom or in shallow, calm waters, are colonies of Nostoc, a blue-green algae (cyanobacteria). While they look slimy, the balls are fairly hard and tough, and can range from a fraction of an inch to larger than a golf ball. These algae are not a concern and do not indicate bad water quality. They are also sometimes seen on damp forest floors and in ditches."