Here are some photos of the mystery ludwigia submerged...
From left to right:L.palustris, L.'unknown' (long peduncle), L. lacrustris
Here are 2 other Ludwigia species that are questionable.
From my understanding....plants from left to right: palustris,'long peduncle',lacrustris,arcuata,sp. 'red', 'unknown', 'unknown'
Closer look at the leaves.
L.sp. 'red' in the middle of both 'unknown'