Plant Quiz Solved: Seaside Arrow-grass (Triglochin maritima)

Congrats and thanks to Justin for correctly identifying this plant as Seaside Arrow-grass (Triglochin maritima).  This unusual and rare species is listed as threatened in Ohio largely due to its ever-shrinking habitat of calcareous fens, marshes, swales and sandy beaches.  It's very similar to another species; Marsh Arrow-grass (T. palustris) which is also rare in Ohio, where they can occasionally grow alongside one another.  Seaside arrow-grass is much larger and more robust containing flowers on shorter, nearly sessile peduncles and six stamens/carpels; while marsh arrow-grass is smaller, thinner and has three stigma/carpels on flowers with longer peduncles. 

*Update*  Some additional clues to the identity of this species is its circumboreal distribution; the fact it is a monocotyledon; and the blurred background contains a diverse display of last year's grasses, sedges, spikerushes and bulrush in a wet, alkaline habitat.

Here is this week's plant quiz.  Take a look at the photograph below and comment with your answer or best guess!  Both plants in the picture are the same thing with the left specimen in full bloom.  Notice the blurred background hinting its typical habitat here in Ohio.  Good luck!