RECORD: Darwin, C. R. 1866-1867. Ipomoea purpurea. CUL-DAR77.97-98. Edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed by Christine Chua and edited by John van Wyhe 2.2023. RN1
NOTE: See record in the Darwin Online manuscript catalogue, enter its Identifier here. Reproduced with permission of the Syndics of Cambridge University Library and William Huxley Darwin. The volumes CUL-DAR 76-79 contain material for Darwin's book Cross and self fertilisation (1876).
[97]
Stigma covered with pollen 1866—67
(Ipomoea purpurea 2d generation ie seeds are of 2d generation of crosses & self)
Stigma covered with pollen
Crossed plants again crossed} self-fert plants again self-fertilised} |
No' fertilise of flowers 33 31
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pods set 32 29 61 producing 293 seed; therefore with average of 4.803 seed per pod |
170 123 293 |
But 4 pods contained only one poor seed & shd be omitted} 4/289; with average 57/289 of 5.070
Stigma with little pollen only on one edge
Crossed plants again crossed} Self-fert plants again self-fertilise}
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No fertilised 33 31 64
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pods set 33 30 63 producing 319 seed; therefore with average of 5.063 |
171 148 319 |
(no difference whatever in rate of generation of seeds produced from much & little pollen.)
But 1 pod produced only one poor seed 1/318; therefore with average of 5.129
Hence under the most favourable, yet fair, view (ie excluding few pods with one seed) excess of pollen gave average of 5.070 & little pollen on one edge gave 5.129: But this is probably accidental, for the two lots of crossed plants gave with little & much pollen exactly same number, when the one poor pod was excluded.—
(The flowers after fertilisation were had been castrated.)
(I might introduce these facts as a note, when I give all precautions for accuracy in making crosses & allude to Gärtner's hint in Kenntniss, about excess of pollen.)
(170 seeds with from excess of pollen weighed 79.67 gr. whilst 170 seeds with from little pollen weighed 79.2 gr. so no difference worth speaking of, & what then is is in favour of much pollen, whilst the excess in number, little as it is, is in favour of little pollen.)
170 seeds spont. fertilised with from the tall crossed plants weighed only 71.7 gr.
[98]
1866—67
Ipomœa purpurea. (of 4th Generation) seed of 2 generations 52, ie seeds are 2d generation. After fertilisation the flowers were castrated.
Crossed plants (six in number in two pots.) 66 fertilised with little & much pollen & again crossed with distinct plants in same pot & gave 65 pods, with 341 seeds, (excluding one pod with one poor seed) we have 65/340 (5.230 average Hence these are rather more than a third of a seed more fertile than the corresponding self-fertile These 6 plants, ie the part which did not grow above the 7 ft states yielded 56 spont: self-fertilised Altogether the six crossed plants, on the stakes produced 121 pods, from artificial & spontaneous fertilisation 64 [+] 56 [=] 121 170 seed of these crossed plants, when fertilised by much pollen weighed 79.68 gr. by little pollen weighed 79.2 gr. (Partly use p. 5 [illeg]) 170 of the spontaneously self-fertilise seeds on these crossed plants, weighed only 71.7 gr.; so that |
Self-fertilised plants (six in number in same two pots) 62 fl. fert. again by pollen of same flower gave 59 pods These 6 plants (ie parts which did not grow above stakes) produced 25 pods, The lesser fertility of these spont. fert flowers than those above fert by own flower's pollen is probably due to their havng been produced last on the plant. Altogether these six plants produced by artificial & spont. fertilisation produced only 84 pods 170 seed of these self-fertilised plants again art. fert. by own flower pollen (most fertilised by little pollen, weighed only 74.2 gr. so 5 gr. less than on left side. Hence these seeds are rather lighter & germinated first see Back. I did not weighed the 105 spont. fert. seed on the self-fert. plants.—
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Citation: John van Wyhe, ed. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)
File last updated 29 May, 2023