Figure 2.

Vein density as a limiter of transpiration. Relationship between vein density and maximum conductance of leaves to water vapour (equivalent to transpiration under standard atmospheric conditions) shown for a mixed sample of tropical and temperate angiosperm (open circles), conifer (filled triangles) and fern (filled circles) leaves measured under natural conditions. Values are means±s.d. A single, highly significant regression (y=0.068 x^0.74; r²=0.87) is fitted to the pooled data since group regressions were not significantly different.