. Heredity and evolution in plants . EVOLUTION 105 viduals measured. The length varied from 8 to 16millimeters, and in the following proportions: Millimeters 8 9 10 n 12 13 14 15 16 Number of beans, i 2 23 108 167 106 33 7 i The beans were then placedin a glass jar divided intonine compartments, all thebeans of the same lengthin the same this was done it wasfound that the beans wereso grouped that the tops ofthe columns in the variouscompartments followed acurve, known as Quetelets1curve (Fig. 51). This curve may be plottedby erecting vertical lines(ordinates) at intervals of
. Heredity and evolution in plants . EVOLUTION 105 viduals measured. The length varied from 8 to 16millimeters, and in the following proportions: Millimeters 8 9 10 n 12 13 14 15 16 Number of beans, i 2 23 108 167 106 33 7 i The beans were then placedin a glass jar divided intonine compartments, all thebeans of the same lengthin the same this was done it wasfound that the beans wereso grouped that the tops ofthe columns in the variouscompartments followed acurve, known as Quetelets1curve (Fig. 51). This curve may be plottedby erecting vertical lines(ordinates) at intervals of onemillimeter on a horizontalline or base, the height ofeach vertical line being pro-portionate to the number ofbeans having the length in- FlG ^.—Demonstration of dicated in figures at its base. Quetelets law of fluctuating varia- This curve shows the freq- bilit> in the length of seeds of thc - • . common bean (Phaseolus vulgaris). uency of occurrence of seeds Description in the any given dimension from de Vries.). (Redrawn 1 So named from its discoverer, Quetelet (Ket-lay). As de Vries states:For a more exact demonstration a correction would be necessary, sinceobviously the larger beans fill up their compartment more than a similarnumber of small ones. io6 i v AND i m\ i\ PLANTS between the two limits or extremes, and is therefore oftenreferred to as a curve of frequency. It should be notedthat, in the case illustrated, the greatest frequency (in-dicated by the highest point of the curve) very nearlycoincides with the average dimension; in other words, themore any given character departs from the average for thatc/iaracter, the less frequent is its occurrence. In another experiment, ears of corn, harvested fromthe same crop, were measured and found to vary in length
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