It looks very much like Fumaria officinalis which I have growing in my garden, I have seedlings at various stages now and one is much like yours chelle except it might be a little more bluish than green.
I've taken a photo of my seedling but won't be downloading it just yet.
http://plants.usda.gov/java/pr...
Corydalis is in the same family.
http://luirig.altervista.org/f...
