Water star grass : An aquatic plant (Schollera graminea) with grassy leaves, and yellow star-shaped blossoms.

Example:


Taxonomy
Water Star Grass, Heteranthera dubia, Nearctica, mud flats, shallow water, leaves, Eastern Wildflowers, Pontederiaceae, species, yellow flowers, Color Photograph, Line Drawing, Britton, A. Brown, Illustrated Flora of the Northern United States and, United States and Canada, Second Edition, Jacq.

Defination from the web:
Water Star Grass (Heteranthera dubia) Color Photograph: Copyright Nearctica.com, Inc. Line Drawing: Britton, N.L., and A. Brown. 1913. ... Habitat: Water Star Grass is found in quiet, shallow water or the mud flats along rivers and lakes. Flowering period: June to September. ...