The lyrics are on the pdmusic.org site (1860, link second column under Maud Irving).
Link:
http://www.pdmusic.org/webster/jpw60itmtr.txt

Still looking for sheet music.

In pdmusic.org, what reference does their code [M1621.W] refer to?

To repeat, there are no botanical names 'emanita' or 'islip', nor are the names known as common or vulgar names for any flowers.

In the lyrics on pdmusic.org, it is the myrtle "with an emerald hue" and the "pale aronatus with eyes so bright blue."

There is no flower with the botanical name 'aronatus'. See Stearn, Botanical Latin. It is not known as a common or vulgar name for a flower.