According to The Plant List:
Epilobium alpinum L. is a synonym of Epilobium palustre L.
And:
Chamerion angustifolium (L.) Holub is a synonym of Epilobium angustifolium L.
So it would appear that Chamerion is now Epilobium
And GRIN, the national germplasm system that we really rely on at the botanical garden, along with The Plant List and ITIS says:
Taxon: Epilobium angustifolium L.
Synonym of Chamaenerion angustifolium subsp. angustifolium
Note: Chamaenerion versus Chamerion --- different spelling??? Arghhhhhh
