Uncertain lichen

Uncertain lichen

Observation - Uncertain lichen - UK and Ireland. Description: I'm pretty sure it's a Cladonia but I'm having a bit of difficulty pinning down which. Growing on livivng oak but more frequent on dead wood. Most often when on living wood, poking up through mat of bryophtyes. Thanks in advance for your help

I'm pretty sure it's a Cladonia but I'm having a bit of difficulty pinning down which. Growing on livivng oak but more frequent on dead wood. Most often when on living wood, poking up through mat of bryophtyes. Thanks in advance for your help