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The relationship between mean conduit pit area (one wall; A), pit aperture area (B), and mean ASP for 10 fern species (gray circles) and two fern allies (white circles). Species with larger pit areas and pit aperture areas were less resistant to increasing lumen air pressure. Error bars indicate sd; r2 = 0.74 in A and 0.47 in B, both excluding P. aquilinum (Pa). For species symbols, see Table I.
