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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    Atropa. I. First Cross-hred Generation. Eeciprocal crosses were made between two individuals of A Bella donna tyjnca (flowers brown, fruits black, stem tinged A;dth red = B) and a vigorous specimen of A. Belladonna, var. htea (flowers and fruits yellow, stem pure green = Y).* Both forms are perennial From crosses of the form B x Y 100 plants were raised, and from the reciprocal unions Y x B, 236. In both sets of cross-breds the fruits (numbering in the three years, during which the plants have been under observation, some thousands) were all black, and though the flowers showed several shades of brown they never varied to pure yellow The stems were more or less deeply tinged. It would appear then that the colour of the type form is completely dominant in the fruit of the cross-bred, but that in the corolla and stem the intensity of the dark coloration may be more or less diminished.t II. Offspnng of Cms-hreds. ^ Twenty-five flowers on as many cross-breds were self-fertilised, but (in consequence perhaps of self-sterility) set no fruit; off'spring were therefore obtained by fertilising the cross-breds with pollen from the parent forms. (a) Cross-hred x Dominant.—Flowers on 21 individuals (20 Y x B and 1 B X Y) were crossed with the dominant form ; 220 (197 and 23) plants were raised, and all bore black fruits. As in the first cross-bred generation there was complete dominance of the type colour. /3. Cross-bred x Becessive.—Flowers on 38 individuals (22 Y x B and 16 Bx Y) were crossed with the recessive form, and the seeds of each plant sown separately. In every case a mixed lot of seedlings was obtained, difl'ering in the colour (green or reddish) of the young stem (hypocotyl). Unfortunately a late frost killed an enormous number of the seedlings, before any attempt had been made to estimate at all accurately the total numbers of the two colours; it had, however, been noted, that up to this time there ajDpeared to be either rough equality or a slight preponderance of the pure green. Of those that survived many perished before flowering, owing to the dryness of the season, so that eventually less than 300 plants lived to bear fruit; of * There was no difficviltj in manipulating this cross, nevertheless few flowers set fruit; 250 were crossed and only about a do/en set seed. The fruits that were formed liad a full complement of seed. f HofPinann obtained a similar result with these two forms ; he states that cross- breds, whether offspring of tjpica x lutea or liitea x typica, in the two seasons during which they were observed bore only black fruits. The experiments were not apparently conlinued beyond the first generation. 'Ber. Oberhessische Gesoll. fiir IS^atur. u. Ileilkunde,' 16, s. 14.