This stitch looks like a chain stitch with a little leg, it is often used for thorny stems in foliage.
It is one of the outline stitches used in Mountmellick embroidery.
Bring the needle up at the top of the line. Go down diagonally to the right and pull through.
Come back up horizontally on the line below the starting point.
Pass the needle under the first diagonal stitch from top right to bottom left.
Go down the same hole of your starting point. Keep the thread in clockwise direction and leave a loop.
Come out at the same hole you came out the second time on the line. Make sure the needle is inside the loop.
Now pull out the needle gently to make a chain. This completes a mountmellick stitch.
Continue with a diagonal stitch to the right.
Come back out on the line.
Pass the thread under the diagonal stitch.
Keep the thread in clockwise direction and take the needle down at the same hole you started the second diagonal stitch. Make a chain as before and continue.
Structure of stitch
Jane Houston-Almqvist, Mountmellick Work (1985, 1990, 1996)
Pat Trott, Beginner’s Guide to Mountmellick Embroidery (2002)
Yvette Stanton & Prue scott, Mountmellick Embroidery Inspired by Nature (2004)