together, the twenty-seven crossed plants were in height to the twenty-seven self-fertilised plants as 100 to 96.  This excess of height in the crossed plants, is so small compared with that displayed by the offspring from the same mother-plants when crossed by a slightly different variety, that we may suspect (as explained under Table 7/C) that most of the individuals belonging to the variety which served as the mother-plants in my experiments, had acquired a nearly similar constitution, so as not to profit by being mutually intercrossed.]

Reviewing these twenty-six cases, in which the crossed plants either do not exceed the self-fertilised by above five per cent in height, or are inferior to them, we may conclude that much the greater number of the cases do not form real exceptions to the rule,—­that a cross between two plants, unless these have been self-fertilised and exposed to nearly the same conditions for many generations, gives a great advantage of some kind to the offspring.  Of the twenty-six cases, at least two, namely, those of Adonis and Bartonia, may be wholly excluded, as the trials were worthless from the extreme unhealthiness of the plants.  Inn twelve other cases (three trials with Eschscholtzia here included) the crossed plants either were superior in height to the self-fertilised in all the other generations excepting the one in question, or they showed their superiority in some different manner, as in weight, fertility, or in flowering first; or again, the cross-fertilised flowers on the mother-plant were much more productive of seed than the self-fertilised.

Deducting these fourteen cases, there remain twelve in which the crossed plants show no well-marked advantage over the self-fertilised.  On the other hand, we have seen that there are fifty-seven cases in which the crossed plants exceed the self-fertilised in height by at least five per cent, and generally in a much higher degree.  But even in the twelve cases just referred to, the want of any advantage on the crossed side is far from certain:  with Thunbergia the parent-plants were in an odd semi-sterile condition, and the offspring grew very unequally; with Hibiscus and Apium much too few plants were raised for the measurements to be trusted, and the cross-fertilised flowers of Hibiscus produced rather more seed than did the self-fertilised; with Vandellia the crossed plants were a little taller and heavier than the self-fertilised, but as they were less fertile the case must be left doubtful.  Lastly, with Pisum, Primula, the three generations of Canna, and the three of Nicotiana (which together complete the twelve cases), a cross between two plants certainly did no good or very little good to the offspring; but we have reason to believe that this is the result of these plants having been self-fertilised and cultivated under nearly uniform conditions for several generations.  The same result followed with the experimental plants of Ipomoea and Mimulus, and to a certain extent with