After the heights of the crossed and self-fertilised plants had been taken, they were sometimes cut down close to the ground, and an equal number of both weighed.  This method of comparison gives very striking results, and I wish that it had been oftener followed.  Finally a record was often kept of any marked difference in the rate of germination of the crossed and self-fertilised seeds,—­of the relative periods of flowering of the plants raised from them,—­and of their productiveness, that is, of the number of seed-capsules which they produced and of the average number of seeds which each capsule contained.

When I began my experiments I did not intend to raise crossed and self-fertilised plants for more than a single generation; but as soon as the plants of the first generation were in flower I thought that I would raise one more generation, and acted in the following manner.  Several flowers on one or more of the self-fertilised plants were again self-fertilised; and several flowers on one or more of the crossed plants were fertilised with pollen from another crossed plant of the same lot.  Having thus once begun, the same method was followed for as many as ten successive generations with some of the species.  The seeds and seedlings were always treated in exactly the same manner as already described.  The self-fertilised plants, whether originally descended from one or two mother-plants, were thus in each generation as closely interbred as was possible; and I could not have improved on my plan.  But instead of crossing one of the crossed plants with another crossed plant, I ought to have crossed the self-fertilised plants of each generation with pollen taken from a non-related plant—­that is, one belonging to a distinct family or stock of the same species and variety.  This was done in several cases as an additional experiment, and gave very striking results.  But the plan usually followed was to put into competition and compare intercrossed plants, which were almost always the offspring of more or less closely related plants, with the self-fertilised plants of each succeeding generation;—­all having been grown under closely similar conditions.  I have, however, learnt more by this method of proceeding, which was begun by an oversight and then necessarily followed, than if I had always crossed the self-fertilised plants of each succeeding generation with pollen from a fresh stock.

I have said that the crossed plants of the successive generations were almost always inter-related.  When the flowers on an hermaphrodite plant are crossed with pollen taken from a distinct plant, the seedlings thus raised may be considered as hermaphrodite brothers or sisters; those raised from the same capsule being as close as twins or animals of the same litter.  But in one sense the flowers on the same plant are distinct individuals, and as several flowers on the mother-plant were crossed by pollen taken from several flowers on the father-plant, such seedlings would