Moulded slime

 The woodland next to the Croft has recently been cut, leaving the tracks covered in wood chips. I run along these tracks most days.

Recently I've tried not to step on this:

Cowpat? Dog vomit? Stale bread roll?

 At first it was yellow and fluffy - I thought it was some effect caused by horse urine. Then it dried out and turned cream-brown, so maybe it was a cowpat (there are no free cows around here, so unlikely)?

 I broke off a piece, and saw the spores, so it had to be a fungus or a mould.

Scores of spores

It turns out that it is a slime mould, Fuligo septica, also known, charmingly, as "dog vomit slime mould". It grows on moist wood chip and mulch. 

Welcome to weird nature!