This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 Excerpt: ...SPECIES. The effect of individual selection on cross-fertilized species, such as corn, is very different from what it is in self-fertilized species. Here the plants chosen are more or less cross-fertilized with other plants and the seeds obtained from a single plant are not all alike in content of hereditary characters ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 Excerpt: ...SPECIES. The effect of individual selection on cross-fertilized species, such as corn, is very different from what it is in self-fertilized species. Here the plants chosen are more or less cross-fertilized with other plants and the seeds obtained from a single plant are not all alike in content of hereditary characters. Hence we may get distinct differences in the individuals grown from this seed. Either mass selection or individual selection in a crop of this character may make decided changes in it for the reason that, in the seed of every plant, combinations of hereditary characters will occur that are unlike those in the original plants selected. Some of these may be superior to the original plants. For instance, the plant with which we start may be heterozygote with reference to a particular character which we will call "A." That is, it inherited from one of its parents the presence of this character and from the other its absence. Its formula with reference to this character would therefore be Aa. Such a plant will produce progeny one-fourth of which has the formula AA, one-half Aa, and one-fourth aa. Now, the combination AA may be superior to Aa and aa, so that in the seed of our selection we may get something better than the plant selected. On the other hand, we may also get something not so good. Selection alone, therefore, enables us to make positive improvements in crops which regularly cross-fertilize. The work done on the corn plant at the Illinois Agricultural Experiment Station is perhaps the best illustration of the effect of selection on crops that cross-fertilize. Bulletin 128 of that station gives the results of ten years' selection of corn for high and low oil content and for high and low protein content. Some of these results ...
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