Reports to the Evolution Committee of the Royal Society. 1-5.

Date:
1902-1910
Catalogue details

Licence: In copyright

Credit: Reports to the Evolution Committee of the Royal Society. 1-5. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    these, all those with green stems bore yellow flowers and fruits, those with reddish steins brown flowers and black fruits, but the latter were more than twice as immerous as the former (197 B, 75 Y). In view of the earlier observation on the seedlings, however, it seems extremely doubtful whether any reliance can be placed upon the final numbers. Although, therefore, all that can be stated with certainty is that there is complete agreement with Mendel's law in so far—(1) that the fruit colour of the type form is completely dominant in the first cross-bred generation, whether the cross be of the form D x R or E x D ; and (2) that the offspring resulting from a union between a cross-bred and a pure dominant are all dominant, but that when the cross is made with a pure recessive the offspring are mixed dominant and recessive; nevertheless, the observations made at the time of germina- tion suggest that this agreement would probably prove quantitative as well as qualitative. Datura. The following forms were employed— 1. JD. Stramonium (stems green, flowers white, fruits prickly), 2. D. Stramonkm, var. inermis (stems green, flowers white, fruits smooth). 3. 1). Tatida (stems reddish, flowers violet, fruits prickly). •i. /A Tatida, var. inermis (stems reddish, flowers violet, fruits smooth). Reciprocal crosses between these different types showed clearly that of the two pairs of antagonistic characters the violet colour is dominant, the white recessive, and similarly that the armed condition is dominant and the unarmed recessive; also that these results obtain whichever combination of forms is employed. Several earlier observers have selected the various species of Datura as affording suitable material for the study of hybrids. Naudin* orossed D. Stramonium with D. Tatida, and D. Taiida with D. Stra- 'iiionium, and found that in both cases the first generation of cross-breds resembled D. Tatula; in the second generation both the parent forms appeared, but D. Tatida was more abundant than D. Stramonium—the -actual figures are not given. Similarly with D. Stramonium and D. Icevis, the first generation resembled D. Stromonium, the second produced both forms. Later Godron'sf results appeared with a record of the numbers obtained. This observer found that D. BertoloniiX crossed with B. Tatula yielded ofi'spring all resembling D. Tatida; but that * ' No\iv. Arcli. Mus.,' 1, p. 41; for the earlier literature, see Focke's ' Pflanzen- MischUiigc,' p. 263. t ' Mem. Acad. Sfcanisl.,' 18G4, 1865, 1872. t -D. Bertolonii of Godroii = D. SLramonium, var. inermis. D. Imvis of Naudin is a wliite-flowered unarmed form not very different from this.