Plant-breeding; comments on the experiments of Nilsson and Burbank . correlation may be looked for in themutual dependency of different organs, the one affordingor controlhng the nourishment for the other. This case,however, though of quite common occurrence, cannot alwaysbe easily separated from the first, botli causes ordinarilycombining their cilorts in the same direction. It may be stuched by the statistical method. A hundredor more individuals are measured, and the result is representedby a single Hne. In order to do this, the individuals arearranged according to the degree of development
Plant-breeding; comments on the experiments of Nilsson and Burbank . correlation may be looked for in themutual dependency of different organs, the one affordingor controlhng the nourishment for the other. This case,however, though of quite common occurrence, cannot alwaysbe easily separated from the first, botli causes ordinarilycombining their cilorts in the same direction. It may be stuched by the statistical method. A hundredor more individuals are measured, and the result is representedby a single Hne. In order to do this, the individuals arearranged according to the degree of development of themeasured quahty. Suppose we compare the amount of sugarin the sugar-beets of a field. This amount can be measuredfor a part of the tissue, without sacrificing the beet, allowingthereby the selection and the ulterior cultivation of the bestsamples. As is generally known the sap is pressed fromthe tissue and after clearing it, the percentage of sugar isdetermined by the method of polarization. In the year1896, I had an opportunity of studying these percentage. Fig. 95. \ariability in the size of the ripe fruits of the Evening-primroseof Lamarck. A. A weak plant with small fruits. B. A tall plant withlarge fruits. 305 3o6 PLANT-BREEDING figures for some 40,000 beets, cultivated on the fields ofMessrs. Kuhn & Co., at Naarden, in Holland, and examinedin their laboratory for purposes of selection. The averagepercentage was , the extremes going up to 19 and comingdown to about 12 per cent. These extremes, however,were comparatively very rare, especially on the upper sideof the group, where only a few individuals reached the verylimit. IMore than one half of all the beets differed less thanone-half per cent from the average, the total number ofroots with 15 to 16 percent sugar being about twenty-twothousand. On both sides of this central group the numberof beets rapidly decreased with the increasing degree ofdeviation from tiic average value. In the same manner the fluctuati
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