Sea urchin?

This is in fact a Mare's tail, properly named Horse's tail (equisetum arvense) and has survived 541 million years to now become a lowly weed.  It has, however, medicinal properties which must not be overlooked!  In medieval times the plant was used for burnishing silver objects - its leaves have a rough feel about them.  We have a patch growing on the farm near a hedgerow not reallly doing any harm to anything so they will probably last til the end of time unless they are built over!