Page:Popular Science Monthly Volume 80.djvu/384

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THE POPULAR SCIENCE MONTHLY

I have drawn the "pure" red very dark, on the supposition that it will be visibly more highly colored than anything yet seen, although this may not prove to be the case. If it is distinguishable, we shall then permanently isolate the red without further trouble; if it is no different from the impure reds, it will only be possible to separate the pure strain by noting the results of numerous crosses made at random.

PSM V80 D384 Diagram of the cross made with the red sunflower.png
Diagram showing the First Cross made with the Red Sunflower, the result obtained in 1911 and the expected result for 1912. Y = yellow-ray factor; R = red-ray factor.

Last year we made various new crosses, especially with the great double "chrysanthemum-flowered" variety obtained from Dreer of Philadelphia. If we can get this red, as we doubtless can, it will be a striking plant, though perhaps less attractive than the single kinds. In tabulating the characters crossed, I enumerated not only the ray color, but also the color of the disc, the size of the heads, and the manner of growth. In the coronatus X lenticularis cross, everything except ray color is the same on both sides, so there is nothing to be noted. In the coronatus X Russian cross, it is quite otherwise. We find that dark disc is uniformly dominant over yellow; the size of the heads in the cross is greater that that of lenticularis, but much less than that of the Russian; and the manner of growth is intermediate, at first simple like the Russian, but eventually branching at the top. It is evident that there is some correlation between the manner of growth and the size of the heads, as a plant could not well support more than one big head of the Russian type. A certain incompatibility between the two varieties seems to be indicated by a number of monstrous (fasciated) plants.

The accompanying diagram shows the Russian coronatus cross in relation to growth form, and in the third line the expected outcome in 1912.