Dichotomous table for gallers on Hydrocotyle vulgaris
by Hans Roskam
1a Leaf blade curled and distorted => 2
1b Leaves with multicellular warts, depressed at the tip ± golden-yellow, later on browned, hardly 1 mm long. Often many on leaf underside, also coalescing into long ridges or crusts, also on petioles and tillers. Synchytrium aureum
2a Weak wrinkling or curling of leaf blade caused by aphids on underside. Aulacorthum solani
2b Leaf blade strongly deflected downwards, curled and dark-green close to the froth-covered nymph. Philaenus spumarius
2c More or less conspicuous, sometimes distorted locally bulge-like swellings on stems or slight archings on leaves, with loosely arranged aecia and spermogonia. Uromyces lineolatus