Tom's right about Al Shigo who always dropped the "i" in arboriculture, and he did use the "parliament" example. I took him to task on that, that the more appropriate comparison is to "horticulture". Would anyone drop the "i" there?
Small points to be sure. I'd keep the "i" in Arboricide, (models of homicide, fratricide, regicide, etc.)
Then again, my usage probably doesn't bear too close an examination. I say "symplastic" and "apoplastic" when they likely should be "symplasmatic" and "apoplasmatic".