The above self-fertilised plants were allowed to fertilise themselves again under a net, yielding self-fertilised plants of the second generation, and the supposed crossed plants were crossed by pollen of a distinct plant; but from want of time this was done in a careless manner, namely, by smearing one head of expanded flowers over another.  I should have thought that this would have succeeded, and perhaps it did so; but the fact of 108 of the self-fertilised seeds weighing 4.87 grains, whilst the same number of the supposed crossed seeds weighed only 3.57 grains, does not look like it.  Five seedlings from each lot of seeds were raised, and the self-fertilised plants, when fully grown, exceeded in average height by a trifle (namely .4 of an inch) the five probably crossed plants.  I have thought it right to give this case and the last, because had the supposed crossed plants proved superior to the self-fertilised in height, I should have assumed without doubt that the former had really been crossed.  As it is, I do not know what to conclude.

Being much surprised at the two foregoing trials, I determined to make another, in which there should be no doubt about the crossing.  I therefore fertilised with great care (but as usual without castration) twenty-four flowers on the supposed crossed plants of the last generation with pollen from distinct plants, and thus obtained twenty-one capsules.  The self-fertilised plants of the last generation were allowed to fertilise themselves again under a net, and the seedlings reared from these seeds formed the third self-fertilised generation.  Both lots of seeds, after germinating on bare sand, were planted in pairs on the opposite sides of two pots.  All the remaining seeds were sown crowded on opposite sides of a third pot; but as all the self-fertilised seedlings in this latter pot died before they grew to any considerable height, they were not measured.  The plants in Pots 1 and 2 were measured when between 7 and 8 inches in height, and the crossed exceeded the self-fertilised in average height by 1.57 inches.  When fully grown they were again measured to the summits of their flower-heads, with the following result:—­

Table 4/31.  Iberis umbellata.

Heights of plants to the summits of their flower-heads, in inches.

Column 1:  Number (Name) of Pot.

Column 2:  Crossed Plants.

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

Pot 1 :  18 :  19. 
Pot 1 :  21 :  21. 
Pot 1 :  18 2/8 :  19 4/8.

Pot 2 :  19 :  16 6/8. 
Pot 2 :  18 4/8 :  7 4/8. 
Pot 2 :  17 6/8 :  14 4/8. 
Pot 2 :  21 3/8 :  16 4/8.

Total :  133.88 :  114.75.

The average height of the seven crossed plants is here 19.12 inches, and that of the seven self-fertilised plants 16.39, or as 100 to 86.  But as the plants on the self-fertilised side grew very unequally, this ratio cannot be fully trusted, and is probably too high.  In both pots a crossed plant flowered before any one of the self-fertilised.  These plants were left uncovered in the greenhouse; but from being too much crowded they were not very productive.  The seeds from all seven plants of both lots were counted; the crossed produced 206, and the self-fertilised 154; or as 100 to 75.