THE BED SUNFLOWER 379 



1910-11 in his greenhouse. They grew to enormous size (being the 

 Eussian X coronatus qto^^) , but when at length they flowered, all the 

 rays were pure yellow! This was indeed disappointing, though we 

 thought we could readily get the red back in the next generation. In 

 the meanwhile, the greater part of the seed was sown in our garden, 

 though some was sent to the English naturalist Dr. A. R. Wallace, who 

 successfully raised the plants. During the summer we went east, but 

 before we left, we noted with hope that some of the young plants 

 showed a great deal of purple in the stems. On our return early in 

 August, a gorgeous sight met our eyes. The sunflowers were in full 

 bloom, and about half were splendidly red ! The reds were by no 

 means uniform, as the accompanying figure shows, some having a ring 

 of red, while others were suffused with red all over, and others showed 

 only a little of the color. Indeed on a single plant there is great varia- 

 tion, and often heads on a genuinely " red " plant may have wholly 

 yellow rays. This results from the fact that the red is produced as the 

 end-result of a chemical process, which seems to be completed only 

 under favorable conditions. Thus a " yellow " head on a red plant dif- 

 fers fundamentally from a true yellow in its make-up, but resembles it, 

 owing to what may be called a lack of opportunity. The controlling 

 factors are not well understood, but even in the case of the original 

 plant, the last small heads of the season were almost entirely yellow- 

 rayed. 



I have said that about half of our sunflowers were of the red type. 

 It was a matter of chance that the four grown in the greenhouse were 

 all yellow. But how can we reconcile these results with Mendel's law? 

 All were crossed with red: if red is dominant, then all should be red; 

 if it is recessive, none 'should. The explanation is, no doubt, that the 

 original plant was a DE, not a DD. This could come about without the 

 existence of earlier red plants, by a variation occurring in a germ-cell, 

 which mated, of course, with one which was normal. Consequently, the 

 original plant, though it may have had no red parent, was in fact a 

 hybrid (or more correctly, mongrel), and we have not yet seen a 

 " 'pure " red. 



The accompanying diagram represents the supposed course of events. 

 The first line (1910) shows the original cross made by us. When YY 

 meets EY, two combinations are possible, and are equally probable, 

 namely, YY (yellow) and EY (red). The result observed in 1911 thus 

 follows naturally. The third line shows what may be obtained in 1912. 

 If the yellows are mated, we get only yellows. We have a few of these 

 already in bud, from seed gathered from the greenhouse plants. If we 

 cross the reds with reds (as has been done in large numbers) we must 

 expect one fourth pure yellows, one half impure reds like the parents 

 (I have drawn only one to save space), and one fourth "pure" reds. 



