OK, the last ingredient for Signurian Vodka is lemon, which is in the lemon tree in the arboretum. With this you can get Titania's Vision Center, on the bar shelf. You need the rowbot to get to the arboretum though.

Also note, the pillar to the right of the monkey in the Parrot Room sneezes. Suspicious?

Starship Titanic Walkthrough
Starship Titanic Review