| Magenta red | Lavender | White faintly tinged | |||
| 1901 | 1st | batch | 19 | 27 | 14 |
| " | 2nd | " | 9 | 20 | 9 |
| 1902 | 1st | " | 12 | 23 | 11 |
| " | 2nd | " | 14 | 26 | 11 |
| — | — | — | |||
| 54 | 96 | 45 |
The numbers 54 : 96 : 45 approach the ratio 1 : 2 : 1 so nearly that there can be no doubt we have here a simple case of Mendelian laws, operating without definite dominance, but rather with blending.
When Laxton speaks of the “remarkably fine but unfixable pea Evolution” we now know for the first time exactly what the phenomenon meant. It, like the “Giant Lavender,” was a “mule” form, not represented by germ-cells, and in each year arose by “self-crossing.”
This is only one case among many similar ones seen in the Chinese Primrose. In others there is no doubt that more complex factors are at work, the subdivision of compound characters, and so on. The history of the “Giant Lavender” goes back many years and is not known with sufficient precision for our purposes, but like all these forms it originated from crossings among the old simple colour varieties of sinensis.
VI. The Argument Built on Exceptions.
So much for the enormous advance that the Mendelian principles already permit us to make. But what does Professor Weldon offer to substitute for all this? Nothing.
Professor Weldon suggests that a study of ancestry will help us. Having recited Tschermak’s exceptions and the great irregularities seen in the Telephone group, he writes:
“Taking these results together with Laxton’s statements, and with the evidence afforded by the Telephone group of hybrids, I think we can only conclude that segregation of seed-characters is not of universal occurrence among cross-bred peas, and that when it does occur, it may or may not follow Mendel’s law.”
Premising that when pure types are used the exceptions form but a small part of the whole, and that any supposed absence of “segregation” may have been variation, this statement is perfectly sound. He proceeds:—
“The law of segregation, like the law of dominance, appears therefore to hold only for races of particular ancestry [my italics]. In special cases, other formulae expressing segregation have been offered, especially by De Vries and by Tschermak for other plants, but these seem as little likely to prove generally valid as Mendel’s formula itself.