374 THE POPULAR SCIENCE MONTHLY 



So far good: but now a diflBeulty arose. On looking up the litera- 

 ture, we found that Dr. G. H. Shull had experimented with sunflowers, 

 and had found them invariably self-sterile. That is to say, no sun- 

 flower would produce seed with its own pollen, even though it came 

 from a different head. Here was a dilemma; there was, so far as we 

 could tell, only one plant of the red sunflower in the world, and this 

 could not be self-fertilized ! The only thing to do was to make crosses 

 with ordinary sunflowers, and see what would come of it. It must now 

 be explained that, aside from the color of the rays, there are many kinds 

 of sunflowers. Putting aside the perennial species and annuals like the 

 small " cucumber-leafed " Helianthus debilis, there are several types 

 closely related to the " common or garden " sunflower, Helianthus 

 annuus. All are called Helianthus, which is simply Greek for sun- 

 flower. The red sunflower found at Boulder belongs to the prairie 

 species, called by some botanists Helianthus lenticularis, by others 

 simply a variety of Helianthus annuus. It is perfectly fertile with the 

 garden strains of annuus, but has a number of marked characteristics. 

 Less robust than the cultivated forms, it branches very freely and pro- 

 duces numerous relatively small heads of flowers. The center, or disc, 

 which is yellow in the big " Eussian " sunflower, is " black," or strictly 

 speaking a dark purplish-red. 



The red sunflower was crossed with the Russian, the wild lenticularis, 

 and with a plant which we took to be a cross, Eussian and lenticularis. 

 All the crosses were made by Mrs. Cockerell, who has in fact done all 

 the work on the red sunflower. The accompanying illustration shows 

 some of the heads covered with bags to protect them from the bees and 

 birds and save the seeds. Crosses could be made either way, that is, 

 using " red " pollen on the other sorts, or other pollen on the red. It 

 was necessary in each case to "bag" the head before it came into 

 flower, and to watch very carefully whenever the bags were off for polli- 

 nation or inspection. The bees are tireless in visiting sunflowers, and 

 scarcely a moment seems to pass during the warm part of the day when 

 an unprotected head is not visited. A single bee might easily spoil an 

 experiment by bringing unaccounted-for pollen, while later small 

 flnches were present in flocks to eat the seeds. All this work was time- 

 consuming and laborious, but there is no other way if exact results are 

 desired. Taking the principal characters, as cited above, we may tabu- 

 late the two main crosses as follows. The name coronatus, now used 

 for the red sunflower, was proposed in Science, 1910, and was sug- 

 gested by a certain resemblance to the sun in eclipse, showing the 

 corona. The sign X signifies a cross. 



(1) CoitoNATus X Lenticularis 

 Red rays X yellow rays 



Dark disc X dark disc 



