Life, I have argued, is not conﬁned within points but proceeds along lines. But does it grow or ﬂow? Should we liken its movement to that of a stream or river as it cuts through the landscape on its way to the sea, or would it better be compared to the stems of plants as they push upwards towards the light? Perhaps these alternatives are not mutually exclusive: after all, the growth of a tree depends on the ﬂow of sap through the bark that sustains it, just as a river brings nourishment and fertility to the land along its banks. Nevertheless throughout the history of the Western world, from classical Antiquity to the present day, hydraulic and arboricultural metaphors have struggled for supremacy, or have sought compromise in the most bizarre and improbable of solutions. Nowhere has this been more apparent than in the practices of genealogy, of tracing the paths of human life from their ancestral sources or roots to their contemporary manifestations. In this brief interlude I turn my attention to the genealogical line.