These are called white turtleheads to tell them from pink or red ones. I guess you only need to say white when not in the presence of the plants. To see a pink one, you can look up Chelone glabra in Wikipedia. The lead image to the right is actually a pink turtlehead. I would alert them to this but I have failed to get them to accept my identifying info. Seems like I keep running into those problems. The other day I tried to make a comment on another blog, and couldn't prove I wasn't a robot.
White turtlehead was used as medicine by Indians to treat worms, eruptions, and to stimulate appetite. Curious combination. It was also used in the hope of preventing pregnancy.