THE SCIENTIFIC MONTHLY
JANUARY, 1922
HYBRIDIZATION IN PLANT AND ANIMAL IMPROVEMENT
By Dr. D. F. JONES
CONNECTICUT AGRICULTURAL EXPERIMENT STATION, NEW HAVEN, CONN.
THE function of hybridization is the rearrangement of already exist ing characters, the bringing together of qualities scattered about in different forms into one or a few individuals which represent the beginning of a new variety, or a new breed. How the common fruits, flowers and vegetables of our gardens and domestic animals in the fields and about the house have been multiplied into endless kinds by a re combination of a relatively few types becomes apparent when the history of any particular group of plants or animals is reviewed.
The dahlia is one of the most popular garden flowers due largely to its easy culture, simple vegetative propagation and the wealth of colors and forms. The fact that the plants can also be easily grown from seed, giving an astonishing array of markedly different flowers, has made this a fascinating subject for experimentation by the amateur gardener and has greatly increased the number of well recognized varieties. The dahlia was first generally cultivated in Europe in 1789 having been introduced from Mexico. At that time the flowers were single and not greatly different from Cosmos and Coreopsis which are its nearest relatives. The first double flowered form was recorded in 1814 at which time there were listed some 12 well marked color types. Twelve years later the number of varieties had increased to 60 due to recombinations of the existing color varieties with the double flowered condition and also new shades of color were brought out by crossing and doubtless by mutation as well.
The first Cactus dahlia came to light in 1879. This form was a radical departure from the common type. The margins of the petals were bent back instead of forward giving the flowers a very distinct appearance and a welcome change from the extreme forms which look too artificial. A small flowered and profusely blooming type known as Pompon was also discovered. There now existed four main types based on flower form: Single, Double, Cactus and Pompon. The double dahlias are classified in two groups by the florists as Show and
