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Show 300 THE EFFECTS OF CROSSING CHAP. VIII. opponents, was well shown by their relative weio·hts when cut down, which was as 100 to 78. Tho 1:ean height of the flower-stems on tho twenty-five intercrossed plants in the ton pots taken to~·othor, was to that of the flower-stems on the twonty-:Hvo self-fertilised plants, as 100 to 92. Thus the intorcrossed plants were certainly sup rior to the soH-fertilised in so.nle degree; but their superiority was s1nnll c01nparcd w1th that of the offspring fro1n a cro. s hot\Yoon distinct plants over the self-fertilis d, this being in the ratio of 100 to 70 in h ight. Nor does this latter ratio sho~ at all fairly the gre~t uporiority of the plants denved from a cross between distinct inclividnals over · the self-fertilised, as tho former produced 1noro than twice as many flower-sten1s as the latter, and were much less liabl tu premature death. \2.) Ipomwa p·urpurea.-Thirty -one in torcrossod plants raised from a cross between flow rs on the smno plants were grown in ten pots in coinpotition with tho same numb r of self-fertilised plants, and tho fonnor were to the latter in height as 100 to 105. So that the self-fertilised plants were a little tc:tller than tho intercrossed; and in eight out of the t n pot· a solf-fortilisecl plant flowered before any one of tho crossed phtnts in the same pots. The plants which were not greatly crowded in nine of tho pots (and these offer the fairest standard of comparison) wore cut down and weighed; and the weight of the twenty-seven intorcrossod plants was to · that of the twenty-seven self-fertilised as 100 to 124; so that by this test tho superiority of the self-fertilised was strongly 1narkod. To this subject of the superiority of the self-fertilised plants in certain cases, I shall have to recur in a futuro chapter. If we n?w. turn to the offspring from a cross between distinct plants when put into co1npetition with self- CHAP. VIII. FLOWERS ON THE SAME PLANT. 301 fertilised plants, we find that the mean height of seventy-three such crossed plants, in the course of ten generations, was to that of the same number of self-fertilised plants as 100 to 77; and in the case of the plants of the tenth generation in weight as 100 to 44. Thus the contrast between the effects of crossing flowers on the same plant, and of crossing flowers on distinct plants, is wonderfully great. (3.) Mi,mulus luteus.-rrwenty-two plants raised by crossing flowers on the sttn1e plant were grown in competition with the same number of self-fertilised plants; and the fanner were to the latter in height as 100 to 105, and in weight as 100 to 103. Moreover, in seven out of the eight pots a self-fertilised plant flowered before any of the intercrossed plants. So that here again the self-fertilised exhibit a slight superiority over the intercrossed plants. For the sake of comparison, I may add that seedlings raised during three generations from a cross between distinct plants were to the self-fertilised plants in height as 100 to 65. ( 4.) Pelargonium zonale.-Two plants growing in separate pots, whieh had been propagated by cuttings from the same plant, and therefore formed in fact parts of the same individual, were intercrossed, and other flowers on one of these plants were self-fertilised; but the seedlings obtained by the two processes did not differ in height. When, on the other hand, flowers on one of the above plants were crossed with pollen taken fro1n a distinct seedling, and other flowers were self-fertilised, the crossed offspring thus obtained were to the self-fertilised in height as 100 to 7 4. (5.) Origanum vulga~re.-A plant which had been long cultivated in my kitchen garden, had spread by stolons so as to form a large bed or clump. Seedlings raised by intercrossing flowers on these plants, which |