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||P.668 right column 3rd paragraph: "When grown in limiting phosphate, the stalks of Caulobacter and Rhodomicrobium elongate from their usual length of ∼1 to 3 μm to as much as 20 μm (primary sources 33, 61, 97, 289). The response is under direct genetic control, because Caulobacter mutants produce elongated stalks even in the presence of sufficient phosphate (primary sources 33, 97)."