What is a genus of hardy perennial flowering plants, of the order Scrophulariaceaæ., natives of North America; -- called also snakehead, turtlehead, shellflower, etc called?

chelone — A genus of hardy perennial flowering plants, of the order Scrophulariaceaæ., natives of North America; -- called also snakehead, turtlehead, shellflower, etc. (Webster's 1913.)

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