Proserpinaca palustris L.
marsh mermaidweed, common mermaidweed
marsh mermaidweed, common mermaidweed
August 25,
Blue Hills Reservation, Braintree
Mermaid-weed has three-merous flowers and three-angled fruit, which makes it different from water-milfoils, plants of the same family that have four-merous flowers and fruit.