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Show 198 PETUNIA VIOLACEA. 0IIAP. VI. from those deduced from the measurements in the followin()' b table:- No. of Pot. TABLE LXXXII. Petunia violacea. Westerham-cros,-ed I I Plants (from Self- Intercrossed Plants .. fertilised Plants of (Plants of on and Self-fert1lt sed Plants Fourth Generation .the same to~k I (self-fertili ed for crossed hy a fresh ~ntercrosse~ for Five Generations). Stock). F1ve Generatwns). ---- - -- - -- Inches. Inches. Inches. I. 64~ 57§ 4-3 ~ 24 64 5 6~ 51~ 58~ 3q --- - II. 48~ 59~ 41 ~ 54~ 58~ 4q 58k 53 1 8~ - III. 62 52§ 46~ 53§ 54* 45 62~ 61~ 19~ --- - IV. 44a 58~ 37 ~ 49g • 6:)~ 33g .. 59~ . 32 ~ - -- -- 43k 35H 4lg 53~ 34-~ 26 ~ v. 53§ 54H 0 I 37 ~ .)6 46 ~ 61 63~ 29 a 0 57~ 14 ~ VI. --- ----- ---- -- 59~ 5l 43 43~ 49R 12g 50~ 0 0 VII. - - ----- -.- 37~ 38g I 2ta 37 ~ 44 ~ 14 ~ VIII. Crowded. - -- -- Total in inches. 1051•25 1190·50 I 607•88 . The twenty-one Westerham-crossed plants now averaged 50·05 Inches; the twenty-two intercrossed plants, 54 ·11 inches; and the twenty-one self-fertilised plants, 33 · 23 inches in hcjght. We thus get the following ratios:- CHAP. VI. CROSS WITH A FRESH STOCK. 199 The Westerham-crossed plants in hejght to the self-fertilised . as 100 to 66 The Westerham-crossed plants in height to the intercrossed . as 100 to 108 The intercrossed plants in height to the self-fertilised . as 100 to 61 We here see that the Westerham-crossed (the offspring of plants self-fertilised for four generations and then crossed with a fresh stock) have gained greatly in height, since they were first measured, relatively to the plants self-fertilised for five generations. They were then as 100 to 91, and now as 100 to 66 in height. The intercrossed plants (i.e., those which had been intercrossed for the last five generations) likewise exceed in height the self-fertilised plants, as occurred in all the previous generations with the exception of the abnormal plants of the third generation. On the other ha.nd, the Westerham-crossed plants are exceeded jn hejght by the intercrossed; and this is a surprisjng fact, judging from most of the other strictly analogous cases. But as the vV ester ham-crossed plants were still growjng vigorously, while the intercrossed had almost ceased to grow, there can hardly be a doubt that if left to grow for another month they would have beaten the intercrossed in height. That they were gaining on them is clear, as when measured before they were as 100 to 119, and now as only 100 to 108 in height. The Westerham-crossed plants had also leaves of a darker green, and looked altogether more vigorous than the intercrossed; and what is much more important, they produced, as we shall presently see, much heavier seed-capsules. So that in fact the offspring from the self-fertilised plants of the fourth generation crossed by a fr8sh stock were superior to the intercrossed, as well as to the self-fertilised plants of the fifth generation--of which latter fact there could not be the least doubt. These three lots of plants were cut down close to the ground and weighed. The twenty-one Wester ham-crossed plants weighed 32 ounces ; the twenty-two intercrossed plants, 34 ounces, and the twenty-one self-fertilised plants 7 i ounces. The following ratios are calculated for an equal number of plants of each kind. But as the self-fertilised plants were just beginning to wither, their relative weight is here slightly too small; and as the Wester hamcrossed were still growing vigorously, their relative weight with time allowed would no doubt have greatly increased. |