Complex sentence: The American Elm "Ulmus americana" cultivar'Incisa' was described by Loudon in 1838 as having "leaves somewhat more deeply serrated and rather smaller" than the type Green, P. S. (1964).
Split into simpler sentences: The American Elm "Ulmus americana" cultivar'Incisa' was first described by Loudon in 1838. The tree had "leaves somewhat more deeply serrated and rather smaller" than the type Green, P. S. (1964).