From the foregoing data it is easy to calculate that: 

Ten Westerham-crossed capsules would have contained 6.26 grains weight of seed.

Ten intercrossed capsules would have contained 4.14 grains weight of seed.

Ten self-fertilised capsules would have contained 3.00 grains weight of seed.

We thus get the following ratios:—­

Seeds from the Westerham-crossed capsules to those from the capsules of the fifth self-fertilised generation, in weight as 100 to 48.

Seeds from the Westerham-crossed capsules to those from the capsules of the fifth intercrossed generation, in weight as 100 to 66.

Seeds from the intercrossed capsules to those from the self-fertilised capsules, in weight as 100 to 72.

So that a cross with pollen from a fresh stock greatly increased the productiveness of the flowers on plants which had been self-fertilised for the four previous generations, in comparison not only with the flowers on the same plants self-fertilised for the fifth time, but with the flowers on the crossed plants crossed with pollen from another plant of the same old stock for the fifth time.

These three lots of seeds were placed on sand, and were planted in an equal state of germination in seven pots, each made tripartite by three superficial partitions.  Some of the remaining seeds, whether or not in a state of germination, were thickly sown in an eighth pot.  The pots were kept in the greenhouse, and the plants trained up sticks.  They were first measured to the tops of their stems when coming into flower; and the twenty-two Westerham-crossed plants then averaged 25.51 inches; the twenty-three intercrossed plants 30.38; and the twenty-three self-fertilised plants 23.40 inches in height.  We thus get the following ratios:—­

The Westerham-crossed plants in height to the self-fertilised as 100 to 91.

The Westerham-crossed plants in height to the intercrossed as 100 to 119.

The intercrossed plants in height to the self-fertilised as 100 to 77.

These plants were again measured when their growth appeared on a casual inspection to be complete.  But in this I was mistaken, for after cutting them down, I found that the summits of the stems of the Westerham-crossed plants were still growing vigorously; whilst the intercrossed had almost, and the self-fertilised had quite completed their growth.  Therefore I do not doubt, if the three lots had been left to grow for another month, that the ratios would have been somewhat different from those deduced from the measurements in Table 6/82.

Table 6/82.  Petunia violacea.

Heights of plants measured in inches.

Column 1:  Number (Name) of Pot.

Column 2:  Westerham-Crossed Plants (from self-fertilised Plants of fourth generation crossed by a fresh stock).

Column 3:  Intercrossed Plants (Plants of one and the same stock intercrossed for five generations).