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Show 192 PETUNIA VIOLACEA. CHAP. VI. had not been sufficiently ripened, and thus produced weakly plants, as oceurred with Iberis. When the crossed plants were between 3 and 4 inches in height, the six finest in four of the pots were measured to the summits of their stems, and at the same time· the six fiuest of the self-fertilised plants. The measurements are given in the preceding table (LXXVIII.), and it may be here Reen that all the self-fertilised I lants exceed their opponents in height, whereas when subsequently measured the excess of the self-fertilised depended chiefly on the unusual tallness of two of the plants in Pot II. The crossed plants here average 3·27, and tho self-fertilised 6·08 inches in height; or as 100 to 186. When fully grown they wore again measured, as follows :- TABLE LXXIX. Petunia violacea ( ThiTd GeneTation; plants fully grown). No. of Pot. Crossed Plants. Self-fertilised Plants. Inches. Inches. I. 41~ 40~ 48 39 36 48 II. 36 47 21 80§ 36 § 86 ~ III. 52 46 IV. 57 43 ~ Total in inches. 327•75 I 431•00 The eight crossed plants now averaged 40 · 96, and the eight self:. fertilised plants 53· 87 inches in height, or as 100 to 131; and this excess chiefly depended, as already stated, on the unusual tallness of two of the self-fertilised plants in Pot II. The selffertilised had therefore lost some of their former great superiority over the crossed plants. In three of the pots the selt:.fertilised plants flowered first; but in Pot III. at the same time witH the crossed. The case is rendered the more strange, because the cross~d plants in the fifth pot (not included in the two last tables), m CHAP. VI. CROSSED AND SELF-FERTILISED PLANTS. 193 which all the remaining seeds had been thickly sown, were from the first finer plants than the self-fertilised, and bad larger leaves. At the period when the two tallest crossed plants in this pot were 6t and 4* inches high, the two tallest self-fertilised were only 4 inches. When the two crossed plants were 12 and 10 inches .high, the two self-fertilised were only 8 inches. These latter plants, as well as many others on the same side of this pot never grew any higher, whereas several of the crossed plants grew to the height of two feet! On account of this great superiority of the crossed plants, the plants on neither side of this pot have been included in the two last tables. Thirty flowers on the crossed plants in Pots I. and IV. (Table LXXIX.) were ~.gain crossed, and produced seventeen capsules. Thirty flowers on the self-fertilised plants in the same two pots were again self-fertilised, but produced only seven capsules. The contents of each capsule of both lots were placed in separate watch-glasses, and the seeds from the crossed appeared to the eye to be at least double the number of those from the selffertilised capsules. In order to ascertain whether the fertility of the self-fertilised plants had been lessened by tbe plants having been self-fertilised for the three previous generations, thirty flowers on the crossed plants were fertilised with their owri pollen. These yielded only five capsules, and their seeds being placed in separate watch-glasses did not seem more numerous than those from the capsules on the self-fertilised plants self-fertilised .for the fourth time. So that as far as can be jndged from so few capsules, the self-fertility of the Eelf-fertilised plants had not decreased in comparison with that of the plants which had been intercrossed during the three previous generations. It should, however, be remembered that hoth lots of plants had been subjected in each generation to almost exactly similar conditions. Seeds from the crossed plants again crossed, and fron1 the selffertilised again self-fertilised, produced by the plants in Pot I. (Table LXXIX.), in which the three self-fertilised plants were on an average only a little taller than the crossed, were used in the following experiment. 'l'bey were kept separate from two similar lots of. seeds produced by the two plants in Pot IV. in the same table, in which the crossed plant was much taller than its self-fertilised opponent. Crossed and se-"lf-fertilised Plants of the Fourth Gene1·ation 0 |
