Sorry - I should have described the scene better Heck I didn't even notice it either (thought it was a discolored streak on the stalk) for a long time. Only when the dragonfly landed directly opposite it did it raise itself off the stalk to reveal its entire outline.
Yes, it is a spider - don't know the species but I've seen quite a few around the ponds - has long "eye stalks" and spins a minimal web. Mostly an ambush spider I suspect.