Trying to ID this plant for a friend. He collected it from a cold water lake in the Eastern Sierra where we live . The tank he has it in is cold water. Any help would be appreciated. Thanks!
It's definitely Myriophyllum. It's not M. aquaticum and from the number of leaflet pairs it's not M. spicatum. Probably either Northern Milfoil (M. sibiricum) or Whorled Milfoil (M. verticillatum).