Leaf stitch (surface)
Imagine or faintly draw a double stem line. Starting at the base of your shape bring your needle up through the fabric on one of the stem lines.
Take the needle to the opposite side of the shape and take it down through the fabric on the line, creating a straight slanted stitch.
Do the same on the opposite side by bringing the needle up through the fabric on the other stem line just under the previous stitch and taking it down on the opposite side of the leaf.
Repeat the process, bringing the needle up just under the previous stitch and above the rest.
Structure of stitch
S. F. A. Caulfield, Blanche C. Saward, The Dictionary of Needlework (1882)
Mrs Archibald Christie, Samplers and Stitches (1921) , p.16
Mary Thomas’s Dictionary of Embroidery Stitches (1934) , p.144–5