 This custom or prescription is either "de modo decimandi", or "de non-decimando".A "modus decimandi", commonly called by the simple name of a "modus" only, is where there is by custom a particular manner of tithing allowed, different from the general law of taking tithes in kind, which are the actual tenth part of the annual increase.This is sometimes a pecuniary compensation, as twopence an acre for the tithe of land