This stitch is the Siennese Stitch. This is the latest stitch from my 100 Stitches list.
For my stitch demonstration, I am using perle cotton floss. This is DMC Color Variations #4022. I set up two parallel guidelines so that I could keep my stitch size consistent.
The first step is to come up through the fabric and form a Straight Stitch.
then come back up through the fabric a small distance from the Straight Stitch:
Pull the floss all the way through and bring the needle around to slide under the Straight Stitch. Make sure your needle passes under the Straight Stitch but then over the working floss - this will create a loop:
Pull the floss all the way until the loop is snug around the first Straight Stitch. Now go back into the fabric and pull all the way through....
and this will complete the stitch!
Continue working the Sienese Stitch along the parallel lines.
When finished, secure your floss on the underside of the fabric. Here is a look at the underside of this stitch:
I learned this stitch from the book Embroidery Stitches by Mary Webb.