The several plants in all my experiments were treated in exactly the same manner, and were carefully protected by fine nets from the access of insects, excepting Thrips, which it is impossible to exclude. I performed all the manipulations myself, and weighed the seeds in a chemical balance; but during many subsequent trials I followed the more accurate plan of counting the seeds. Some of the capsules contained no seeds, or only two or three, and these are excluded in the column headed "good capsules" in several of the following tables:--

TABLE 1.6. Primula veris.

Column 1: Nature of the Union. Column 2: Number of Flowers fertilised. Column 3: Number of Capsules produced. Column 4: Number of good Capsules. Column 5: Weight of Seed in grains. Column 6: Calculated Weight of Seed from 100 good Capsules.

Long-styled by pollen of short-styled. Legitimate union : 22 : 15 : 14 : 8.8 : 62.

Long-styled by own-form pollen. Illegitimate union : 20 : 8 : 5 : 2.1 : 42.

Short-styled by pollen of long-styled. Legitimate union : 13 : 12 : 11 : 4.9 : 44.

Short-styled by own-form pollen. Illegitimate union : 15 : 8 : 6 : 1.8 : 30.

SUMMARY:

The two legitimate unions : 35 : 27 : 25 : 13.7 : 54.

The two illegitimate unions : 35 : 16 : 11 : 3.9 : 35.

The results may be given in another form (Table 1.7) by comparing, first, the number of capsules, whether good or bad, or of the good alone, produced by 100 flowers of both forms when legitimately and illegitimately fertilised; secondly, by comparing the weight of seed in 100 of these capsules, whether good or bad; or, thirdly, in 100 of the good capsules.

TABLE 1.7. Primula veris.

Column 1: Nature of the Union. Column 2: Number of Flowers fertilised. Column 3: Number of Capsules. Column 4: Number of good Capsules. Column 5: Weight of Seed in grains. ... Column 6: Number of Capsules. Column 7: Weight of Seed in grains. ... Column 8: Number of good Capsules. Column 9: Weight of Seed in grains.

The two legitimate unions : 100 : 77 : 71 : 39 :: 100 : 50 :: 100 : 54.

The two illegitimate unions : 100 : 45 : 31 : 11 :: 100 : 24 :: 100 : 35.

We here see that the long-styled flowers fertilised with pollen from the short- styled yield more capsules, especially good ones (i.e. containing more than one or two seeds), and that these capsules contain a greater proportional weight of seeds than do the flowers of the long-styled when fertilised with pollen from a distinct plant of the same form. So it is with the short-styled flowers, if treated in an analogous manner. Therefore I have called the former method of fertilisation a legitimate union, and the latter, as it fails to yield the full complement of capsules and seeds, an illegitimate union. These two kinds of union are graphically represented in Figure 1.2.

(FIGURE 1.2. Primula veris. Graphic representation of two kinds of union between: Left: Long-styled form. Right: Short-styled form.)

If we consider the results of the two legitimate unions taken together and the two illegitimate ones, as shown in Table 1.7, we see that the former compared with the latter yielded capsules, whether containing many seeds or only a few, in the proportion of 77 to 45, or as 100 to 58. But the inferiority of the illegitimate unions is here perhaps too great, for on a subsequent occasion 100 long-styled and short-styled flowers were illegitimately fertilised, and they together yielded 53 capsules: therefore the rate of 77 to 53, or as 100 to 69, is a fairer one than that of 100 to 58. Returning to Table 1.7, if we consider only the good capsules, those from the two legitimate unions were to those from the two illegitimate in number as 71 to 31, or as 100 to 44. Again, if we take an equal number of capsules, whether good or bad, from the legitimately and illegitimately fertilised flowers, we find that the former contained seeds by weight compared with the latter as 50 to 24, or as 100 to 48; but if all the poor capsules are rejected, of which many were produced by the illegitimately fertilised flowers, the proportion is 54 to 35, or as 100 to 65.

The Different Forms of Flowers on Plants of the Same Species Page 13

19th Century English Literature

Charles Darwin

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Charles Darwin

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