“One Million Seed Types,” by Mark Fischetti and Accurat [Graphic Science; July 2020], includes a legend that states, “Area indicates number of seeds for that genus.” It seems more likely to me that it indicates the number of seed samples. Otherwise the circles would not fall into neat size units.

SIMON LEVAY West Hollywood, Calif.

THE EDITORS REPLY: The circle sizes in the graphic reflect the number of seeds per genus (as correctly labeled) rather than the number of seed samples. But LeVay brings up an excellent point that we did not address directly on the page: The circles do fall into suspiciously “neat size units.” To fit them on a grid—and to make the smallest seed collections visible—the scale that informed their size was based on ranges instead of continuous values. Each circle’s area was calculated according to seed numbers. But those numbers were first consolidated into discrete bins for best fit, with the aid of an algorithm.

This article was originally published with the title “Letters” in Scientific American 323, 5, 8-10 (November 2020)