Crossed and self-fertilised plants of the seventh generation.

Crossed and self-fertilised seeds from the crossed and self-fertilised plants of the sixth generation were sown in the usual manner on opposite sides of three pots, and the seedlings were well and equally thinned.  Every one of the self-fertilised plants (and many were raised) in this, as well as in the eighth and ninth generations, belonged to the tall white variety.  Their uniformity of character, in comparison with the seedlings first raised from the purchased seed, was quite remarkable.  On the other hand, the crossed plants differed much in the tints of their flowers, but not, I think, to so great a degree as those first raised.  I determined this time to measure the plants on both sides carefully.  The self-fertilised seedlings came up rather before the crossed, but both lots were for a time of equal height.  When first measured, the average height of the six tallest crossed plants in the three pots was 7.02, and that of the six tallest self-fertilised plants 8.97 inches, or as 100 to 128.  When fully grown the same plants were again measured, with the result shown in Table 3/18.

Table 3/18.  Mimulus luteus (Seventh Generation).

Heights of Plants in inches: 

Column 1:  Number (Name) of Pot.

Column 2:  Crossed Plants.

Column 3:  Self-fertilised Plants.

Pot 1 :  11 2/8 :  19 1/8. 
Pot 1 :  11 7/8 :  18.

Pot 2 :  12 6/8 :  18 2/8. 
Pot 2 :  11 2/8 :  14 6/8.

Pot 3 :  9 6/8 :  12 6/8. 
Pot 3 :  11 6/8 :  11.

Total :  68.63 :  93.88.

The average height of the six crossed is here 11.43, and that of the six self-fertilised 15.64, or as 100 to 137.

As it is now evident that the tall white variety transmitted its characters faithfully, and as the self-fertilised plants consisted exclusively of this variety, it was manifest that they would always exceed in height the crossed plants which belonged chiefly to the original shorter varieties.  This line of experiment was therefore discontinued, and I tried whether intercrossing two self-fertilised plants of the sixth generation, growing in distinct pots, would give their offspring any advantage over the offspring of flowers on one of the same plants fertilised with their own pollen.  These latter seedlings formed the seventh generation of self-fertilised plants, like those in the right hand column in Table 3/18; the crossed plants were the product of six previous self-fertilised generations with an intercross in the last generation.  The seeds were allowed to germinate on sand, and were planted in pairs on opposite sides of four pots, all the remaining seeds being sown crowded on opposite sides of Pot 5 in Table 3/19; the three tallest on each side in this latter pot being alone measured.  All the plants were twice measured—­the first time whilst young, and the average height of the crossed plants to that of the self-fertilised was then as 100 to 122.  When fully grown they were again measured, as in Table 3/19.