https://c8.alamy.com/comp/PG15HX/fossil-plants-for-students-of-botany-and-geology-paleobotany-fig-245-a-marattia-fraxinea-a-a-single-synangium-showing-the-two-valves-and-pores-of-the-sporangial-compartments-b-b-it-kaulfussii-c-kaulfussia-synangium-showing-pores-of-sporangial-compart-ments-d-b-marattiopsis-milnsteri-c-after-hooker-d-e-after-schimper-composed-of-two-valves-which-on-ripening-come-apart-and-expose-two-rows-of-pores-formed-by-the-apical-dehiscence-of-the-sporangial-com-partments-fig-245-a-b-in-marattia-kaulfussii-the-sori-are-attached-to-the-lamina-by-a-short-stalk-fig-PG15HX.jpg