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Show 214 NICOTIANA TAB.A.CUM. CHAP. VI. TABLE XC. Nicotiana tabacum. Plants raised from the same seeds as in the last two experiments, but sown separately in the open ground, so as not to compete together. From Pot II., Table LXXXVII. From Pot V., Table LXXXVII. - --- - Ke w -crossed Plants of the Kew-crossed Plants of the Plauts. Fourth elf-ferti- Plants. Fourth , 'clf-fcrti-lised Generation. li ed Gcncratiou. -- - Inches. Inches. Inches. Inches. ~~ 2g 22a 54~ 34~ 54~ • 37 a .51~ 38~ 39~ 34~ 45 40~ 53g 30 43 43§ 49~ 28~ 43 40 .1)0 ~ 31 ~ 48R 38g 47 A 25~ 44 35a 57~ 26 g 48g 39~ 37 22~ 55k 47R 48 28 63 !)8~ 478•75 286•86 II -- 496 •13 417·25 The twenty tallest crossed plants here average 48·74, and the twenty tallest self-fertilised 35 · 2 inches in height; or as 100 to 72. These plants after being measured were cut down close to the ground, and tho twenty crossed plantR weighed 195·75 ounces, and the twenty self-fertilised plants 123 · 25 ounces; or as 100 to 63. In the three preceding tables, LXXXVIII., LXXXIX., and XC., we have the measurements of fifty-~ix plants derived from two plants of the third self-fertilised generation crossed with pollen from a fr.esh stock, and of fifty-six plants of the fourth self- . fertilised generation derived from the same two plants. These crossed and self-~ertilised plants were treated in three different ways, having been put, firstly, into moderately close competition with one another in pots; secondly, having been subjected to unfavourable conditions and to very severo competition from being greatly crowded in two large pots; and thirdly, having being sown separately in open and good ground, so as not to suffer from any mutual competition. In all these cases the crossed plants in each lot were greatly superior to the Eelf- CHAP. VI. CYCLAMEN PERSICU:M. 215 fertilised. This was shown in several ways,-by the earlier germinatjon of the crossed seeds, by the mo~e rapid ?rowth of the seedlings whilst quite young, by the earher flowenng of the mature plant~, as well as by the greater height which they ultimately attained. The superiority of the crossed plants was shown still more plainly when the two lots were weighed; the weight of the crossed plants to that of the self-fertilised in the two crowded pots being as 100 to 37. Better evidence could hardly be desired of the immense advantage derived from a cross with a fresh stock. XXVI. PRIMULACE.l:E.-CYCLAMEN PERSICUM.* Ten flowers crossed with pollen from plants known to be distinct seedlings, yielded nine capsules, containing on an average 34 · 2 seeds, with a maximum of seventy-seven in one. Ten flowers se)f-fertilised yielded eight capsules, containing on an average only 13 ·1 seeds, with a maximum of twenty-five in one. This gives a ratio of 100 to 38 for the average number of seeds per capsule for the crossed and self-fertilised flowers. The flowers hang downwards, and as the stigmas stand close beneath the anthers, it might have been expected that pollen would have fallen on them, and that they would have been spontaneously self-fertilised; but these covered-up plants did not produce a single capsule. On some other occasions uncovered plants in · the same greenhouse produced plenty of capsules, and I suppose that the flowers had been visited by bees, which could hardly fail to carry pollen from plant oo plant. The seeds obtained in the manner just described were placed on sand, and after germinating were planted in pairs,-three crossed and three self-fertilised plants on the opposite sides of four pots. vVhen the leaves were 2 or 3 inches in length, including the foot-stalks, the seedlings on both sides were equal. In the course of a month or two the crossed plants began to show a slight superiority over the self-fertilised, which steadily increased; and the crossed flowered in aJl four pots some weeks before and much more profusely than the self-fertilised. The two tallest flower-stems on the crossed plants in each pot were now measured, and the average height of the eight stems * Cyclamen repandttm, according to Locoq (' Geogmpbie Botanique de l'Europe,' tom. viii. 1858, p. 150), is protern.ndrous, and this I believe to be the case with C. persicum. |
