Keys to species Ulva

1	Plants reticulate, netlike nature obscuring blade, mostly unattached entangled with other algae	U. reticulata
1	Plants not reticulate, clearly blade like, mostly attached	2
2	Plants normally divided into narrow segments; in transverse section cells along the paler central portion of the older segments much taller than those near the margins	U. fasciata
2	Plants simple or with broad lobes ............	3
3	Blades not naturally perforate; cells in transverse sections nearly square or taller than broad	U. lactuca
3	Blades regularly perforate; cells much broader than tall in section	U. profunda