Replica plating spatial correspondence

Replica plating spatial correspondence is the preserved association between a master site and its sampled sites on replicas. Label a master site by an ordered pair $(r,c)$, specifying its row and column. Keeping the same orientation and viewing convention makes that label refer to the same source on every plate. The biological colonies need not have identical outlines, because the transferred samples can contain different numbers of biological cells.

A simple orientation check shows why a circular outline is insufficient. In a constructed four-by-four layout, a half-turn sends $(r,c)$ to $(5-r,5-c)$. Thus B2, or $(2,2)$, would be confused with C3, or $(3,3)$. Applying the half-turn twice returns the original ordered pair, but applying it once generally selects the wrong source. An asymmetric orientation mark fixes that ambiguity. Two contact transfers also preserve the handedness when all plates are viewed from the same side: any reflection in going from plate to fabric is undone in going from fabric to plate. A fabric-side view must not be silently substituted for a plate-side view.