The Effects of Cross & Self-Fertilisation in the Vegetable Kingdom · Charles Darwin
CHAPTER VII.
SUMMARY OF THE HEIGHTS AND WEIGHTS OF THE CROSSED AND SELF-FERTILISED PLANTS. Number of species and plants measured. Tables given. Preliminary remarks on the offspring of plants crossed by a fresh stock. Thirteen cases specially considered. The effects of crossing a self-fertilised plant either by another self-fertilised plant or by an intercrossed plant of the old stock. Summary of the results. Preliminary remarks on the crossed and self-fertilised plants of the same stock. The twenty-six exceptional cases considered, in which the crossed plants did not exceed greatly in height the self-fertilised. Most of these cases shown not to be real exceptions to the rule that cross-fertilisation is beneficial. Summary of results. Relative weights of the crossed and self-fertilised plants. The details which have been given under the head of each species are so numerous and so intricate, that it is necessary to tabulate the results. In Table 7/A, the number of plants of each kind which were raised from a cross between two individuals of the same stock and from self-fertilised seeds, together with their mean or average heights, are given. In the right hand column, the mean height of the crossed to that of the self-fertilised plants, the former being taken as 100, is shown. To make this clear, it may be advisable to give an example. In the first generation of Ipomoea, six plants derived from a cross between two plants were measured, and their mean height is 86.00 inches; six plants derived from flowers on the same parent-plant fertilised with their own pollen were measured, and their mean height is 65.66 inches. From this it follows, as shown in the right hand column, that if the mean height of the crossed plants be taken as 100, that of the self-fertilised plants is 76. The same plan is followed with all the other species.
The crossed and self-fertilised plants were generally grown in pots in competition with one another, and always under as closely similar conditions as could be attained. They were, however, sometimes grown in separate rows in the open ground. With several of the species, the crossed plants were again crossed, and the self-fertilised plants again self-fertilised, and thus successive generations were raised and measured, as may be seen in Table 7/A. Owing to this manner of proceeding, the crossed plants became in the later generations more or less closely inter-related. In Table 7/B the relative weights of the crossed and self-fertilised plants, after they had flowered and had been cut down, are given in the few cases in which they were ascertained. The results are, I think, more striking and of greater value as evidence of constitutional vigour than those deduced from the relative heights of the plants. The most important table is Table 7/C, as it includes the relative heights, weights, and fertility of plants raised from parents crossed by a fresh stock (that is, by non-related plants grown under different conditions), or by a distinct sub-variety, in comparison with self-fertilised plants, or in a few cases with plants of the same old stock intercrossed during several generations. The relative fertility of the plants in this and the other tables will be more fully considered in a future chapter.
TABLE 7/A. Relative heights of plants from parents crossed with pollen from other plants of the same stock, and self-fertilised. Heights of plants measured in inches. Column 1: Name of Plant. Column 2: Number of Crossed Plants measured. Column 3: Average Height of Crossed Plants. Column 4: Number of Self-fertilised Plants measured. Column 5: Average Height of Self-fertilised Plants. Column 6: x, where the ratio of the Average Height of the Crossed to the Self-fertilised Plants is expressed as 100 to x. Ipomoea purpurea--first generation: 6 : 86.00 : 6 : 65.66 : 76. Ipomoea purpurea--second generation: 6 : 84.16 : 6 : 66.33 : 79. Ipomoea purpurea--third generation: 6 : 77.41 : 6 : 52.83 : 68. Ipomoea purpurea--fourth generation: 7 : 69.78 : 7 : 60.14 : 86. Ipomoea purpurea--fifth generation: 6 : 82.54 : 6 : 62.33 : 75. Ipomoea purpurea--sixth generation: 6 : 87.50 : 6 : 63.16 : 72. Ipomoea purpurea--seventh generation: 9 : 83.94 : 9 : 68.25 : 81. Ipomoea purpurea--eighth generation: 8 : 113.25 : 8 : 96.65 : 85. Ipomoea purpurea--ninth generation: 14 : 81.39 : 14 : 64.07 : 79. Ipomoea purpurea--tenth generation: 5 : 93.70 : 5 : 50.40 : 54. Ipomoea purpurea--Number and average height of all the plants of the ten generations: 73 : 85.84 : 73 : 66.02 : 77.
Mimulus luteus--three first generations, before the new and taller self-fertilised variety appeared: 10 : 8.19 : 10 : 5.29 : 65. Digitalis purpurea: 16 : 51.33 : 8 : 35.87 : 70. Calceolaria--(common greenhouse variety): 1 : 19.50 : 1 : 15.00 : 77. Linaria vulgaris: 3 : 7.08 : 3 : 5.75 : 81. Verbascum thapsus: 6 : 65.34 : 6 : 56.50 : 86. Vandellia nummularifolia--crossed and self-fertilised plants, raised from perfect flowers: 20 : 4.30 : 20 : 4.27 : 99. Vandellia nummularifolia--crossed and self-fertilised plants, raised from perfect flowers: second trial, plants crowded: 24 : 3.60 : 24 : 3.38 : 94. Vandellia nummularifolia--crossed plants raised from perfect flowers, and self-fertilised plants from cleistogene flowers: 20 : 4.30 : 20 : 4.06 : 94. Gesneria pendulina: 8 : 32.06 : 8 : 29.14 : 90. Salvia coccinea: 6 : 27.85 : 6 : 21.16 : 76. Origanum vulgare: 4 : 20.00 : 4 : 17.12 : 86. Thunbergia alata: 6 : 60.00 : 6 : 65.00 : 108. Brassica oleracea: 9 : 41.08 : 9 : 39.00 : 95. Iberis umbellata--the self-fertilised plants of the third generation: 7 : 19.12 : 7 : 16.39 : 86. Papaver vagum: 15 : 21.91 : 15 : 19.54 : 89. Eschscholtzia californica--English stock, first generation: 4 : 29.68 : 4 : 25.56 : 86.
Eschscholtzia californica--English stock, second generation: 11 : 32.47 : 11 : 32.81 : 101. Eschscholtzia californica--Brazilian stock, first generation: 14 : 44.64 : 14 : 45.12 : 101. Eschscholtzia californica--Brazilian stock, second generation: 18 : 43.38 : 19 : 50.30 : 116. Eschscholtzia californica--average height and number of all the plants of Eschscholtzia: 47 : 40.03 : 48 : 42.72 : 107. Reseda lutea--grown in pots: 24 : 17.17 : 24 : 14.61 : 85. Reseda lutea--grown in open ground : 8 : 28.09 : 8 : 23.14 : 82. Reseda odorata--self-fertilised seeds from a highly self-fertile plant, grown in pots: 19 : 27.48 : 19 : 22.55 : 82. Reseda odorata--self-fertilised seeds from a highly self-fertile plant, grown in open ground: 8 : 25.76 : 8 : 27.09 : 105. Reseda odorata--self-fertilised seeds from a semi-self-fertile plant, grown in pots: 20 : 29.98 : 20 : 27.71 : 92. Reseda odorata--self-fertilised seeds from a semi-self-fertile plant, grown in open ground: 8 : 25.92 : 8 : 23.54 : 90. Viola tricolor: 14 : 5.58 : 14 : 2.37 : 42. Adonis aestivalis: 4 : 14.25 : 4 : 14.31 : 100. Delphinium consolida: 6 : 14.95 : 6 : 12.50 : 84. Viscaria oculata: 15 : 34.50 : 15 : 33.55 : 97. Dianthus caryophyllus--open ground, about : 6?: 28? : 6?: 24? : 86.
Dianthus caryophyllus--second generation, in pots, crowded: 2 : 16.75 : 2 : 9.75 : 58. Dianthus caryophyllus--third generation, in pots: 8 : 28.39 : 8 : 28.21 : 99. Dianthus caryophyllus--offspring from plants of the third self-fertilised generation crossed by intercrossed plants of the third generation, compared with plants of fourth self-fertilised generation: 15 : 28.00 : 10 : 26.55 : 95. Dianthus caryophyllus--number and average height of all the plants of Dianthus: 31 : 27.37 : 26 : 25.18 : 92. Hibiscus africanus: 4 : 13.25 : 4 : 14.43 : 109. Pelargonium zonale: 7 : 22.35 : 7 : 16.62 : 74. Tropaeolum minus: 8 : 58.43 : 8 : 46.00 : 79. Limnanthes douglasii: 16 : 17.46 : 16 : 13.85 : 79. Lupinus luteus--second generation: 8 : 30.78 : 8 : 25.21 : 82. Lupinus pilosus--plants of two generations: 2 : 35.50 : 3 : 30.50 : 86. Phaseolus multiflorus: 5 : 86.00 : 5 : 82.35 : 96. Pisum sativum: 4 : 34.62 : 4 : 39.68 : 115. Sarothamnus scoparius--small seedlings: 6 : 2.91 : 6 : 1.33 : 46. Sarothamnus scoparius--the three survivors on each side after three years’ growth: : 18.91 : : 11.83 : 63. Ononis minutissima: 2 : 19.81 : 2 : 17.37 : 88. Clarkia elegans: 4 : 33.50 : 4 : 27.62 : 82.
Bartonia aurea: 8 : 24.62 : 8 : 26.31 : 107. Passiflora gracilis: 2 : 49.00 : 2 : 51.00 : 104. Apium petroselinum: * : : * : : 100. *not measured. Scabiosa atro-purpurea: 4 : 17.12 : 4 : 15.37 : 90. Lactuca sativa--plants of two generations: 7 : 19.43 : 6 : 16.00 : 82. Specularia speculum: 4 : 19.28 : 4 : 18.93 : 98. Lobelia ramosa--first generation: 4 : 22.25 : 4 : 18.37 : 82. Lobelia ramosa--second generation: 3 : 23.33 : 3 : 19.00 : 81. Lobelia fulgens--first generation: 2 : 34.75 : 2 : 44.25 : 127. Lobelia fulgens--second generation: 23 : 29.82 : 23 : 27.10 : 91. Nemophila insignis--half-grown: 12 : 11.10 : 12 : 5.45 : 49. Nemophila insignis--the same fully-grown: : 33.28 : : 19.90 : 60. Borago officinalis: 4 : 20.68 : 4 : 21.18 : 102. Nolana prostrata: 5 : 12.75 : 5 : 13.40 : 105. Petunia violacea--first generation: 5 : 30.80 : 5 : 26.00 : 84. Petunia violacea--second generation: 4 : 40.50 : 6 : 26.25 : 65. Petunia violacea--third generation: 8 : 40.96 : 8 : 53.87 : 131. Petunia violacea--fourth generation: 15 : 46.79 : 14 : 32.39 : 69. Petunia violacea--fourth generation, from a distinct parent: 13 : 44.74 : 13 : 26.87 : 60.
Petunia violacea--fifth generation: 22 : 54.11 : 21 : 33.23 : 61. Petunia violacea--fifth generation, in open ground: 10 : 38.27 : 10 : 23.31 : 61. Petunia violacea--Number and average height of all the plants in pots of Petunia: 67 : 46.53 : 67 : 33.12 : 71. Nicotiana tabacum--first generation: 4 : 18.50 : 4 : 32.75 : 178. Nicotiana tabacum--second generation: 9 : 53.84 : 7 : 51.78 : 96. Nicotiana tabacum--third generation: 7 : 95.25 : 7 : 79.60 : 83. Nicotiana tabacum--third generation but raised from a distinct plant: 7 : 70.78 : 9 : 71.30 : 101. Nicotiana tabacum--Number and average height of all the plants of Nicotiana: 27 : 63.73 : 27 : 61.31 : 96. Cyclamen persicum: 8 : 9.49 : 8?: 7.50 : 79. Anagallis collina: 6 : 42.20 : 6 : 33.35 : 69. Primula sinensis--a dimorphic species: 8 : 9.01 : 8 : 9.03 : 100. Fagopyrum esculentum--a dimorphic species: 15 : 38.06 : 15 : 26.13 : 69. Beta vulgaris--in pots: 8 : 34.09 : 8 : 29.81 : 87. Beta vulgaris--in open ground: 8 : 30.92 : 8 : 30.70 : 99. Canna warscewiczi--plants of three generations: 34 : 35.98 : 34 : 36.39 : 101. Zea mays--in pots, whilst young, measured to tips of leaves: 15 : 20.19 : 15 : 17.57 : 87.
Zea mays--when full-grown, after the death of some, measured to tips of leaves: : 68.10 : : 62.34 : 91. Zea mays--when full-grown, after the death of some, measured to tips of flowers: : 66.51 : : 61.59 : 93. Zea mays--grown in open ground, measured to tips of leaves: 10 : 54.00 : 10 : 44.55 : 83. Zea mays--grown in open ground, measured to tips of flowers: : 53.96 : : 43.45 : 80. Phalaris canariensis--in pots. 11 : 38.90 : 11 : 35.69 : 92. Phalaris canariensis--in open ground: 12 : 35.78 : 12 : 33.50 : 93. TABLE 7/B.--Relative weights of plants from parents crossed with pollen from distinct plants of the same stock, and self-fertilised. Column 1: Names of plants. Column 2: Number of crossed plants. Column 3: Number of self-fertilised plants. Column 4: x, where the ratio of the Weight of the Crossed to the Self-fertilised Plants is expressed as 100 to x. Ipomoea purpurea--plants of the tenth generation: 6 : 6 : 44. Vandellia nummularifolia--first generation: 41 : 41 : 97. Brassica oleracea--first generation: 9 : 9 : 37. Eschscholtzia californica--plants of the second generation: 19 : 19 : 118. Reseda lutea--first generation, grown in pots: 24 : 24 : 21. Reseda lutea--first generation, grown in open ground: 8 : 8 : 40.
Reseda odorata--first generation, descended from a highly self-fertile plant, grown in pots: 19 : 19 : 67. Reseda odorata--first generation, descended from a semi-self-fertile plant, grown in pots: 20 : 20 : 99. Dianthus caryophyllus--plants of the third generation: 8 : 8 : 49. Petunia violacea--plants of the fifth generation, in pots: 22 : 21 : 22. Petunia violacea--plants of the fifth generation, in open ground: 10 : 10 : 36. TABLE 7/C.--Relative heights, weights, and fertility of plants from parents crossed by a fresh stock, and from parents either self-fertilised or intercrossed with plants of the same stock. Column 1: Names of the plants and nature of the experiments. Column 2: Number of plants from a cross with a fresh stock. Column 3: Average height in inches and weight. Column 4: Number of the plants from self-fertilised or intercrossed parents of the same stock. Column 5: Average height in inches and weight. Column 4: x, where the ratio of the Height, Weight and Fertility of the plants from the Cross with a fresh stock is expressed as 100 to x. Ipomoea purpurea--offspring of plants intercrossed for nine generations and then crossed by a fresh stock, compared with plants of the tenth intercrossed generation: 19 : 84.03 : 19 : 65.78 : 78. Ipomoea purpurea--offspring of plants intercrossed for nine generations and then crossed by a fresh stock, compared with plants of the tenth intercrossed generation, in fertility: .. : .. : .. : .. : 51.
Mimulus luteus--offspring of plants self-fertilised for eight generations and then crossed by a fresh stock, compared with plants of the ninth self-fertilised generation: 28 : 21.62 : 19 : 10.44 : 52. Mimulus luteus--offspring of plants self-fertilised for eight generations and then crossed by a fresh stock, compared with plants of the ninth self-fertilised generation, in fertility: .. : .. : .. : .. : 3. Mimulus luteus--offspring of plants self-fertilised for eight generations and then crossed by a fresh stock, compared with the offspring of a plant self-fertilised for eight generations, and then intercrossed with another self-fertilised plant of the same generation: 28 : 21.62 : 27 : 12.20 : 56. Mimulus luteus--offspring of plants self-fertilised for eight generations and then crossed by a fresh stock, compared with the offspring of a plant self-fertilised for eight generations, and then intercrossed with another self-fertilised plant of the same generation, in fertility: .. : .. : .. : .. : 4. Brassica oleracea--offspring of plants self-fertilised for two generations and then crossed by a fresh stock, compared with plants of the third self-fertilised generation, by weight: 6 : : 6 : : 22. Iberis umbellata--offspring from English variety crossed by slightly different Algerine variety, compared with the self-fertilised offspring of the English variety: 30 : 17.34 : 29 : 15.51 : 89.
Iberis umbellata--offspring from English variety crossed by slightly different Algerine variety, compared with the self-fertilised offspring of the English variety, in fertility: .. : .. : .. : .. : 75. Eschscholtzia californica--offspring of a Brazilian stock crossed by an English stock, compared with plants of the Brazilian stock of the second self-fertilised generation: 19 : 45.92 : 19 : 50.30 : 109. Eschscholtzia californica--offspring of a Brazilian stock crossed by an English stock, compared with plants of the Brazilian stock of the second self-fertilised generation, in weight: .. : .. : .. : .. : 118. Eschscholtzia californica--offspring of a Brazilian stock crossed by an English stock, compared with plants of the Brazilian stock of the second self-fertilised generation, in fertility: .. : .. : .. : .. : 40. Eschscholtzia californica--offspring of a Brazilian stock crossed by an English stock, compared with plants of the Brazilian stock of the second intercrossed generation, in height: 19 : 45.92 : 18 : 43.38 : 94. Eschscholtzia californica--offspring of a Brazilian stock crossed by an English stock, compared with plants of the Brazilian stock of the second intercrossed generation, in weight: .. : .. : .. : .. : 100. Eschscholtzia californica--offspring of a Brazilian stock crossed by an English stock, compared with plants of the Brazilian stock of the second intercrossed generation, in fertility: .. : .. : .. : .. : 45.
Dianthus caryophyllus--offspring of plants self-fertilised for three generations and then crossed by a fresh stock, compared with plants of the fourth self-fertilised generation: 16 : 32.82 : 10 : 26.55 : 81. Dianthus caryophyllus--offspring of plants self-fertilised for three generations and then crossed by a fresh stock, compared with plants of the fourth self-fertilised generation, in fertility: .. : .. : .. : .. : 33. Dianthus caryophyllus--offspring of plants self-fertilised for three generations and then crossed by a fresh stock, compared with the offspring of plants self-fertilised for three generations and then crossed by plants of the third intercrossed generation: 16 : 32.82 : 15 : 28.00 : 85. Dianthus caryophyllus--offspring of plants self-fertilised for three generations and then crossed by a fresh stock, compared with the offspring of plants self-fertilised for three generations and then crossed by plants of the third intercrossed generation, in fertility: .. : .. : .. : .. : 45. Pisum sativum--offspring from a cross between two closely allied varieties, compared with the self-fertilised offspring of one of the varieties, or with intercrossed plants of the same stock: ? : : ? : : 60 to 75. Lathyrus odoratus--offspring from two varieties, differing only in colour of their flowers, compared with the self-fertilised offspring of one of the varieties: in first generation: 2 : 79.25 : 2 : 63.75 : 80.
Lathyrus odoratus--offspring from two varieties, differing only in colour of their flowers, compared with the self-fertilised offspring of one of the varieties: in second generation: 6 : 62.91 : 6 : 55.31 : 88. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth self-fertilised generation, in height: 21 : 50.05 : 21 : 33.23 : 66. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth self-fertilised generation, in weight: .. : .. : .. : .. : 23. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth self-fertilised generation, grown in open ground, in height: 10 : 36.67 : 10 : 23.31 : 63. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth self-fertilised generation, grown in open ground, in weight: .. : .. : .. : .. : 53. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth self-fertilised generation, grown in open ground, in fertility: .. : .. : .. : .. : 46. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth intercrossed generation, in height: 21 : 50.05 : 22 : 54.11 : 108.
Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth intercrossed generation, in weight: .. : .. : .. : .. : 101. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth intercrossed generation, grown in open ground, in height: 10 : 36.67 : 10 : 38.27 : 104. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth intercrossed generation, grown in open ground, in weight: .. : .. : .. : .. : 146. Petunia violacea--offspring of plants self-fertilised for four generations and then crossed by a fresh stock, compared with plants of the fifth intercrossed generation, grown in open ground, in fertility: .. : .. : .. : .. : 54. Nicotiana tabacum--offspring of plants self-fertilised for three generations and then crossed by a slightly different variety, compared with plants of the fourth self-fertilised generation, grown not much crowded in pots, in height: 26 : 63.29 : 26 : 41.67 : 66. Nicotiana tabacum--offspring of plants self-fertilised for three generations and then crossed by a slightly different variety, compared with plants of the fourth self-fertilised generation, grown much crowded in pots, in height: 12 : 31.53 : 12 : 17.21 : 54.
Nicotiana tabacum--offspring of plants self-fertilised for three generations and then crossed by a slightly different variety, compared with plants of the fourth self-fertilised generation, grown much crowded in pots, in weight: .. : .. : .. : .. : 37. Nicotiana tabacum--offspring of plants self-fertilised for three generations and then crossed by a slightly different variety, compared with plants of the fourth self-fertilised generation, grown in open ground, in height: 20 : 48.74 : 20 : 35.20 : 72. Nicotiana tabacum--offspring of plants self-fertilised for three generations and then crossed by a slightly different variety, compared with plants of the fourth self-fertilised generation, grown in open ground, in weight: .. : .. : .. : .. : 63. Anagallis collina--offspring from a red variety crossed by a blue variety, compared with the self-fertilised offspring of the red variety: 3 : 27.62 : 3 : 18.21 : 66. Anagallis collina--offspring from a red variety crossed by a blue variety, compared with the self-fertilised offspring of the red variety, in fertility: .. : .. : .. : .. : 6. Primula veris--offspring from long-styled plants of the third illegitimate generation, crossed by a fresh stock, compared with plants of the fourth illegitimate and self-fertilised generation: 8 : 7.03 : 8 : 3.21 : 46. Primula veris--offspring from long-styled plants of the third illegitimate generation, crossed by a fresh stock, compared with plants of the fourth illegitimate and self-fertilised generation, in fertility: .. : .. : .. : .. : 5.
Primula veris--offspring from long-styled plants of the third illegitimate generation, crossed by a fresh stock, compared with plants of the fourth illegitimate and self-fertilised generation, in fertility in following year: .. : .. : .. : .. : 3.5. Primula veris--(equal-styled, red-flowered variety)--offspring from plants self-fertilised for two generations and then crossed by a different variety, compared with plants of the third self-fertilised generation: 3 : 8.66 : 3 : 7.33 : 85. Primula veris--(equal-styled, red-flowered variety)--offspring from plants self-fertilised for two generations and then crossed by a different variety, compared with plants of the third self-fertilised generation, in fertility: .. : .. : .. : .. : 11. In these three tables the measurements of fifty-seven species, belonging to fifty-two genera and to thirty great natural families, are given. The species are natives of various parts of the world. The number of crossed plants, including those derived from a cross between plants of the same stock and of two different stocks, amounts to 1,101; and the number of self-fertilised plants (including a few in Table 7/C derived from a cross between plants of the same old stock) is 1,076. Their growth was observed from the germination of the seeds to maturity; and most of them were measured twice and some thrice. The various precautions taken to prevent either lot being unduly favoured, have been described in the introductory chapter. Bearing all these circumstances in mind, it may be admitted that we have a fair basis for judging of the comparative effects of cross-fertilisation and of self-fertilisation on the growth of the offspring.
Text from Project Gutenberg, public domain in the United States.