hidden triangles

I love to knit socks, but they are mostly my inbetween projects. I pick them up whenever I don't have anything else to knit or need a break from a more complicated pattern. That's why most of my socks are plain stockinette.
But that can get a bit boring so with these socks I tried a little purl stitch design-triangles! What, you can't see any triangles in the pic? Just bumpy spots? Neither can I since they are hidden ;-)

btw. the yarn is self-dyed!

Janin
orangmerajut.blogspot.com