Stervc has kindly provided us with a definition of a parcel, from the Tax Assessor himself: "Kirk told me that a parcel is defined as a boundary of land that has a Tax ID Number affixed to it. So in other words, an area of land that taxes are paid on. He told me that they determine that. He said that a parcel could be 1 acre of land or 160 acres of land like what exists in a spot up north or even more."
So a parcel is a piece of land, not a package or a Christmas present. It's simple. And in Mendocino County you are allowed 25 plants on a parcel, period.