Crossed and self-fertilised plants of the fourth generation.

Seedlings raised as before from the crossed and self-fertilised plants of the third generation in Table 2/3, gave results as follows:—­

Table 2/5.  Ipomoea purpurea (Fourth Generation).

Heights of Plants in inches: 

Column 1:  Number (Name) of Pot.

Column 2:  Crossed Plants.

Column 3:  Self-fertilised Plants.

Pot 1 :  84 :  80. 
Pot 1 :  47 :  44 1/2.

Pot 2 :  83 :  73 1/2. 
Pot 2 :  59 :  51 1/2.

Pot 3 :  82 :  56 1/2. 
Pot 3 :  65 1/2 :  63. 
Pot 3 :  68 :  52.

Total :  488.5 :  421.0.

Here the average height of the seven crossed plants is 69.78 inches, and that of the seven self-fertilised plants 60.14; or as 100 to 86.  This smaller difference relatively to that in the former generations, may be attributed to the plants having been raised during the depth of winter, and consequently to their not having grown vigorously, as was shown by their general appearance and from several of them never reaching the summits of the rods.  In Pot 2, one of the self-fertilised plants was for a long time taller by two inches than its opponent, but was ultimately beaten by it, so that all the crossed plants exceeded their opponents in height.  Of twenty-eight capsules produced by the crossed plants fertilised by pollen from a distinct plant, each contained on an average 4.75 seeds; of twenty-seven self-fertilised capsules on the self-fertilised plants, each contained on an average 4.47 seeds; so that the proportion of seeds in the crossed and self-fertilised capsules was as 100 to 94.

Some of the same seeds, from which the plants in Table 2/5 had been raised, were planted, after they had germinated on damp sand, in a square tub, in which a large Brugmansia had long been growing.  The soil was extremely poor and full of roots; six crossed seeds were planted in one corner, and six self-fertilised seeds in the opposite corner.  All the seedlings from the latter soon died excepting one, and this grew to the height of only 1 1/2 inches.  Of the crossed plants three survived, and they grew to the height of 2 1/2 inches, but were not able to twine round a stick; nevertheless, to my surprise, they produced some small miserable flowers.  The crossed plants thus had a decided advantage over the self-fertilised plants under this extremity of bad conditions.

Crossed and self-fertilised plants of the fifth generation.

These were raised in the same manner as before, and when measured gave the following results:—­

Table 2/6.  Ipomoea purpurea (Fifth Generation).

Heights of Plants in inches: 

Column 1:  Number (Name) of Pot.