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Show 302 THE EFFECTS OF CROSSING C IIAP. VIII. strictly consisted of the same plant, and other scedlin()'s raised froin self-fertilised flowers, were carefully co~pared from their earliest youth to maturity; and they did not differ at all in height or in constitutional vigour. So1ne :flowers on these seedlings wore then crossed with pollen taken from a distinct seedling, and other flowers were self-fertilised; two fresh lots of seedlings being thus raised, which were the grandchildren of the plant that had spread by stolons and formed a large chunp in my garden. The. o differed much in height, the crossed plants beino· to the self-fertilised as 100 to 86. They differed, also, to a wonderful degree in constitutional vigour. The crossed plants flowered first, and produced exactly twice as many flower-stems ; and they afterwards increased by stolons to such an extent as almost to overwhdn1 the self-fertilised plants. Reviewing these five cas s, we see that in four of them, the effect of a cross bet ween flowers on the same plant (even on offsets of the same plant growing on separate roots, as with the Pclargoniu1n and Origanum) does not differ from that of the strictest selffertilisation. Indeed, in two of the cases tho self-fertilised plants were superior to such intercrossod plants. With Digitalis a cross between the flowers on the same plant certainly did do some good, yet very slight compared with that from a cross between distinct plants. On the whole the results here arrived at, if we bear in mind that the flower-buds ·are to a certain extent distinct individuals and occasionally vary independently of one another, agree well with our general conclusion, that the advantages of a cross depend on the progenitors of the crossed plants possessing some· what different constitutions' either fr01n having be. en exposed to different conditions, or to their having CHAP. VIII: FLOWERS ON rrHE SAME PLANT. 303 varied from unknown causes in a manner which we in our ignorance are forced to speak of as spontaneous. Hereafter I shall have to recur to this subject of the inefficiency of a cross between the flowers on the same plant, when we consider the part which insects play in the cross-fertilisation of flowers. On the Transmission of the _qood Effects from a Gross and of the evil Effects from Selfjertilisation.-We have seen that seedlings from a cross between distinct plants a.lmost always exceed their self-fertilised opponents in height, weight, and constitutional vigour, and, as will hereafter be shown, often in fertility. To ascertain . whether this superiority would be transmitted beyond the first generation, seedlings were raise l on three occasions from crossed and self-fertilised plants, both sets being fertilised in the same manner, and therefore not as in the many cases given in Tables A, B, and C, in which the crossed plants were again crossed and the self-fertilised again self-fertilised. Firstly, seedlings were raised from self-fertilised seeds produced under a net by crossed and self-fertilised plants of Nemophila insignis ; and the latter were to the former in height as 133 to 100. But these seedlings became very unhealthy early in life, and grew so unequally that some of them in both lots were five times as tall as the others. Therefore this ex periment was ·quito worthless; but I have felt bound to giv~ it, as opposed to my general conclusion. I should state that in this and the two following trials, both sets of plants .were grown on the opposite sides of the same pots, and treated in all respects alike. '~f.lhe details of the experiments rna y be found under the .head of each species. Secondly, a crossed and a self-fertilised plant of Heartsease (Viola tricolor) grew near together in the |