The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom Part 6

Column 1: Number (Name) of Pot.

Column 2: Colchester-Crossed Plants.

Column 3: Intercrossed Plants of the Tenth Generation.

Pot 1 : 87 : 78.

Pot 1 : 87 4/8 : 68 4/8.

Pot 1 : 85 1/8 : 94 4/8.

Pot 2 : 93 6/8 : 60.

Pot 2 : 85 4/8 : 87 2/8.

Pot 2 : 90 5/8 : 45 4/8.

Pot 3 : 84 2/8 : 70 1/8.

Pot 3 : 92 4/8 : 81 6/8.

Pot 3 : 85 : 86 2/8.

Pot 4 : 95 6/8 : 65 1/8.

Pot 5 : 90 4/8 : 85 6/8.

Pot 5 : 86 6/8 : 63.

Pot 5 : 84 : 62 6/8.

Pot 6 : 90 4/8 : 43 4/8.

Pot 6 : 75 : 39 6/8.

Pot 6 : 71 : 30 2/8.

Pot 6 : 83 6/8 : 86.

Pot 6 : 63 : 53.

Pot 6 : 65 : 48 6/8.

Crowded plants in a very large pot.

Total : 1596.50 : 1249.75.

In sixteen out of these nineteen pairs, the Colchester-crossed plant exceeded in height its intercrossed opponent. The average height of the Colchester-crossed is 84.03 inches, and that of the intercrossed 65.78 inches; or as 100 to 78. With respect to the fertility of the two lots, it was too troublesome to collect and count the capsules on all the plants; so I selected two of the best pots, 5 and 6, and in these the Colchester-crossed produced 269 mature and half-mature capsules, whilst an equal number of the intercrossed plants produced only 154 capsules; or as 100 to 57. By weight the capsules from the Colchester-crossed plants were to those from the intercrossed plants as 100 to 51; so that the former probably contained a somewhat larger average number of seeds.]

We learn from this important experiment that plants in some degree related, which had been intercrossed during the nine previous generations, when they were fertilised with pollen from a fresh stock, yielded seedlings as superior to the seedlings of the tenth intercrossed generation, as these latter were to the self-fertilised plants of the corresponding generation. For if we look to the plants of the ninth generation in Table 2/10 (and these offer in most respects the fairest standard of comparison) we find that the intercrossed plants were in height to the self-fertilised as 100 to 79, and in fertility as 100 to 26; whilst the Colchester-crossed plants are in height to the intercrossed as 100 to 78, and in fertility as 100 to 51.

[THE DESCENDANTS OF THE SELF-FERTILISED PLANT, NAMED HERO, WHICH APPEARED IN THE SIXTH SELF-FERTILISED GENERATION.

In the five generations before the sixth, the crossed plant of each pair was taller than its self-fertilised opponent; but in the sixth generation (Table 2/7, Pot 2) the Hero appeared, which after a long and dubious struggle conquered its crossed opponent, though by only half an inch. I was so much surprised at this fact, that I resolved to ascertain whether this plant would transmit its powers of growth to its seedlings.

Several flowers on Hero were therefore fertilised with their own pollen, and the seedlings thus raised were put into compet.i.tion with self-fertilised and intercrossed plants of the corresponding generation.

The three lots of seedlings thus all belong to the seventh generation.

Their relative heights are shown in Tables 2/14 and 2/15.

TABLE 2/14. Ipomoea purpurea.

Heights of Plants in inches:

Column 1: Number (Name) of Pot.

Column 2: Self-fertilised Plants of the Seventh Generation, Children of Hero.

Column 3: Self-fertilised Plants of the Seventh Generation.

Pot 1 : 74 : 89 4/8.

Pot 1 : 60 : 61.

Pot 1 : 55 2/8 : 49.

Pot 2 : 92 : 82.

Pot 2 : 91 6/8 : 56.

Pot 2 : 74 2/8 : 38.

Total : 447.25 : 375.50.

The average height of the six self-fertilised children of Hero is 74.54 inches, whilst that of the ordinary self-fertilised plants of the corresponding generation is only 62.58 inches, or as 100 to 84.

TABLE 2/15. Ipomoea purpurea.

Heights of Plants in inches:

Column 1: Number (Name) of Pot.

Column 2: Self-fertilised Plants of the Seventh Generation, Children of Hero.

Column 3: Intercrossed Plants of the Seventh Generation.

Pot 3 : 92 : 76 6/8.

Pot 4 : 87 : 89.

Pot 4 : 87 6/8 : 86 6/8.

Total : 266.75 : 252.50.

Here the average height of the three self-fertilised children of Hero is 88.91 inches, whilst that of the intercrossed plants is 84.16; or as 100 to 95. We thus see that the self-fertilised children of Hero certainly inherit the powers of growth of their parents; for they greatly exceed in height the self-fertilised offspring of the other self-fertilised plants, and even exceed by a trifle the intercrossed plants,--all of the corresponding generation.

Several flowers on the self-fertilised children of Hero in Table 2/14 were fertilised with pollen from the same flower; and from the seeds thus produced, self-fertilised plants of the eighth generation (grandchildren of Hero) were raised. Several other flowers on the same plants were crossed with pollen from the other children of Hero. The seedlings raised from this cross may be considered as the offspring of the union of brothers and sisters. The result of the compet.i.tion between these two sets of seedlings (namely self-fertilised and the offspring of brothers and sisters) is given in Table 2/16.

TABLE 2/16. Ipomoea purpurea.

Heights of Plants in inches:

Column 1: Number (Name) of Pot.

Column 2: Self-fertilised Grandchildren of Hero, from the Self-fertilised Children. Eighth Generation.

Column 3: Grandchildren from a cross between the self-fertilised children of Hero. Eighth Generation.

Pot 1 : 86 6/8 : 95 6/8.