Plants growing in the same pots, and subjected in each generation to the same conditions, were intercrossed for nine consecutive generations.  These intercrossed plants thus became in the later generations more or less closely inter-related.  Flowers on the plants of the ninth intercrossed generation were fertilised with pollen taken from a fresh stock, and seedlings thus raised.  Other flowers on the same intercrossed plants were fertilised with pollen from another intercrossed plant, producing seedlings of the tenth intercrossed generation.  These two sets of seedlings were grown in competition with one another, and differed greatly in height and fertility.  For the offspring from the cross with a fresh stock exceeded in height the intercrossed plants in the ratio of 100 to 78; and this is nearly the same excess which the intercrossed had over the self-fertilised plants in all ten generations taken together, namely, as 100 to 77.  The plants raised from the cross with a fresh stock were also greatly superior in fertility to the intercrossed, namely, in the ratio of 100 to 51, as judged by the relative weight of the seed-capsules produced by an equal number of plants of the two sets, both having been left to be naturally fertilised.  It should be especially observed that none of the plants of either lot were the product of self-fertilisation.  On the contrary, the intercrossed plants had certainly been crossed for the last ten generations, and probably, during all previous generations, as we may infer from the structure of the flowers and from the frequency of the visits of humble-bees.  And so it will have been with the parent-plants of the fresh stock.  The whole great difference in height and fertility between the two lots must be attributed to the one being the product of a cross with pollen from a fresh stock, and the other of a cross between plants of the same old stock.

This species offers another interesting case.  In the five first generations in which intercrossed and self-fertilised plants were put into competition with one another, every single intercrossed plant beat its self-fertilised antagonist, except in one instance, in which they were equal in height.  But in the sixth generation a plant appeared, named by me the Hero, remarkable for its tallness and increased self-fertility, and which transmitted its characters to the next three generations.  The children of Hero were again self-fertilised, forming the eighth self-fertilised generation, and were likewise intercrossed one with another; but this cross between plants which had been subjected to the same conditions and had been self-fertilised during the seven previous generations, did not effect the least good; for the intercrossed grandchildren were actually shorter than the self-fertilised grandchildren, in the ratio of 100 to 107.  We here see that the mere act of crossing two distinct plants does not by itself benefit the offspring.  This case is almost the converse of that in the last paragraph,