Hi, Lizz,
Your picture is of the fertile stem of the Field Horsetail Equisetum arvense. Later the green sterile stem will emerge. It is the only species of horsetail in Caithness that has two forms - in all the other species the fertile cone appears at the top of the green stem. Horsetails are fascinating plants. There are 8 species in Caithness and several hybrids. We have the only known location in the world (St John's Loch) for the hybrid Equisetum x mchaffii.