258 MUTATION AND PLANT BREEDING 



Flower Bulbs 



Another category of vegetatively propagated plants where spon- 

 taneous mutations have had, and indeed still have, a great commer- 

 cial importance is the ornamental bulb plants, particularly tulips and 

 hyacinths, but also iris, daffodils, lilies, freesias, and others. The 

 variety collections are continuously enriched by new, and at least 

 sometimes improved variations of the old standard varieties. Let us 

 take one example of such a "mutation family", that of the Bartigon 

 tulip. This old and popular variety is now found in the catalogs as 

 a double-flowered form, "Double Bartigon"; as a parrot form, "Red 

 Champion"; as a giant or "maximum" mutation, "Bartigon Max"; 

 as a white-variegated type, "Cordell Hull"; and as a series of new 

 color sports, including salmon red "Queen of the Bartigons", scarlet 

 red, "All Bright", deep rose "Philip Snowden", etc. 



The flower bulbs have also been the object of some relatively 

 successful experiments with induced mutations, primarily by de Mol 

 in Holland who described his results in a long series of papers. He 

 summarizes the results of the first 13 years of X-ray experiments with 

 tulips and hyacinths (74, 75). More than 70 different cases of induced 

 changes are described, found in about 30 different varieties. The 

 mutations mostly concerned flower color, but flower shape was also 

 involved, ranging from highly irregular monstrosities to rather slight 

 changes, e.g., from rounded to more angular flowers. 



During 1933-34 he irradiated in all 1,472 bulbs belonging to 

 60 different varieties, using 1,200 r units of X-rays. In this material 

 he later isolated 41 different mutations out of 25 of the varieties. Most 

 of these mutations seem to have been cultivated further on in pure 

 condition. 



De Mol was aAvare that the older spontaneous sports may be 

 periclinal chimaeras, e.g., the parrot-tulip Gemma, and that a 

 radiation-induced reversion to the mother type, La Reine, was not a 

 true mutation from the genetical point of view but as a "modifica- 

 tion", or rather as a tissue recombination. But he also induced 

 changed color in parrot tulips without loss of the parrot character, 

 and also new parrot types from normal varieties. Except for a few 

 possible tissue recombinations, most of de Mol's changes obviously 

 were original mutations. 



In a special chapter, at the end of his 1944 paper (74), de Mol 



