Parental plants grown in a greenhouse (a "common garden") at low elevation show a continuous range of heights (above, bottom graph). Cuttings from the same plants (which therefore have the same genotypes) grown at middle and high elevations show a range of heights that are not predictable from the growth pattern at low elevation. For example, genotype #4 does best at medium elevation; genotypes ##1 & 6 do well at high elevation but not medium elevations.

    A related species shows a cline (continuous gradient) of variation in height, depending on the altitude at which it grows. The experiments together indicate that height is a non-linear function of both genotype and environment.