io8 PLANT HYBRIDIZATION BEFORE MENDEL 



From Laxton's cross of 1866, it appears that dominance of 

 round form for cotyledons was evident in the cross, since he says : 



"This cross produced a pod containing five round, white peas, exactly 

 like the ordinary 'Ringleader' seeds." {ib., p. 10.) 



Purple flower color, and color in the seed-coats, was dominant 

 in the 1867-grown plants. 



The seed-coat color of the F^^, however, which was "maple" in 

 the male parent, split into maple (the majority), and violet or 

 deep-purple (a few), in the following generation, grown in 1868. 



The F2 progeny, in 1868, split up into plants with purple 

 flowers and colored seed-coats, and a recessive with white flowers 

 and white seed-coats, which latter bred true in 1868 and 1869. 

 Of the purple-flowered progeny of the F2, the seed-coats were 

 mostly- maple or some modification of it. A few had violet seed- 

 coats. The former, in 1869, split into a majority with seed-coats 

 purple or grey, and only a minority maple or brown-streaked. 

 The "few" in the F2 with violet seed-coats, split, in the F3, into 

 (almost entirely) purplish-grey or maple, with occasional ones 

 violet again. Without further speculation as to the probabilities 

 in respect to the original maple seed-coat color, which Laxton 

 was dealing with in the male parent of the cross, the facts above 

 are given for whatever interest they may have. It should be men- 

 tioned that the seeds, in what we know as the Fg generation, are 

 described as being "partly indented, a few round." It is not clear 

 whether Laxton meant by "partly indented," the same thing as in 

 the description "slightly indented,"' by which the seeds of the 

 original "Maple" parent are described. It may be taken to mean 

 simply that a part of the seeds were indented ; a few round. The 

 expectation would have been, "mostly round, a few indented," 

 to use Laxton's manner of describing. 



The dominance of taljness in the F^ is shown, and the clear 

 segregation out of dwarf with white flower color and white seed- 

 coats in the F2. 



Laxton adds that he had derived from his experiments the 

 same conclusion as Knight and others: 



"That the colors of the envelopes of the seeds of peas immediately 

 resulting from a cross are never changed." (p. 12.) He states also: "I 

 find, however, that the color and probably the substance of the cotyle- 

 dons are sometimes, but not always, changed by the cross-fertilization 

 of two different varieties." (p. 12.) 



