Found a plant on a trip to the river (didn't have my camera ) that looks like a vetch, has the same sort of leaf and growth but it was tangled up with lots of other grasses and sweet clovers so no idea about roots. It has a cluster of tiny back seeds on the end of the branches, no pods at all. Seeds are about the size of poppy seed, only black. There were lots and lots of these things and on several different plants so it seems this is the way these plants set seed; not an aberration from insect damage or disease.
I haven't been able to find anything at all that looks like a vetch but produces this sort of seedball sort of form..all of the vetches and clovers and alfalfa seem to be supposed to have pods of some sort. Since those are all just now beginning to set seed this was clearly flowering some time ago and so I have no idea what the flowers looked like. There was a vetch type of flower I had spotted earlier in other areas (wish I had marked them so I could find them again and check!) which is apparently busy setting seed now so this MIGHT have been the same. Every seed cluster was on the tip of the branch, none further down.
I'll be going back to get water in a week or so so if they're still there I will try to get some photos, if needed. Anyone have any ideas?