Some plants reproduce by forming buds on bulb scales, cuttings of leaves, or stems. Among these are lily bulbs, African violets, and some types of begonias. Easter lily bulbs are made up of scales attached at the base only. When scales are removed from the bulb they soon form small bulblets on the basal end. In order to double the chromosome numbers of lilies, the scales should be soaked, as soon as detached, in a colchicine solution for about 2 hours. They should then be dried, dusted in either Arasan or Fermate, to protect against rot, and planted. If this is done in the North, by the middle of August the scales can be planted outdoors. They can be handled relatively later in the South, but treatment should not be delayed much beyond late October.

It is advisable to plant the scales about 1 to 2 inches deep and at least 3 inches apart so the plants coming from each scale can be identical and examined. A scale may produce both tetraploid and normal bulblets. It is relatively easy to distinguish the affected bulblets as soon as they produce leaves. Such bulblets are greatly retarded in growth and their leaves are usually rather narrow and very thick. Usually the difference in thickness between leaves on normal and affected bulblets can be detected by merely feeling the leaves between the fingers. Eventually the affected individuals start to grow and usually they produce large plants by maturity. If lily scales are handled in this manner, the small bulblets May be dug and replanted in September of the year following treatment, or left in the soil for 2 years. In cold sections it is advisable to place some sort of mulch over the scales and bulblets; about 2 inches of straw will do. It should not be applied until the ground freezes.

A fairly high proportion of the bulblets formed on such treated scales will be tetraploids. Some freak bulblets also will form. In these, some of the cells may have a double chromosome number and some a normal. These types may continue to grow and even flower. Usually their flowers, are distinctly abnormal.

The Easter lily tetraploids so far made demonstrate the importance of treating as many different varieties as possible. All have larger flowers than normal, but some have a much greater increase in size than others.

When a tetraploid lily has been secured, it should be propagated by scaling. Even if it is fertile it can only be reproduced true to type by scales, since Easter lilies do not come true from seed.

The chromosome number of African violets has also been doubled by colchicine treatment. This plant is easy to propagate by leaf cuttings. The leaves are removed with about an inch and a half of stem attached. Several leaves may be bunched together and the bases of their stemsset in a colchicine solution for about 2 hours. They should then be removed and dried and the bases dusted with either Arasan or Fermate to prevent rotting. The cuttings should then be placed in sand. This is best done by setting the stems in a slanting trench with the base of each leaf just touching the sand. New plants are formed at the bottom of the stem, and usually some will have the doubled chromosome number. The few tetraploid African violets we have developed did not show any improvement over the normal.

The concentration of colchicine giving best results may vary considerably for different plants. In lilies, good results have been had with a 0.2-percent solution. African violets responded well to both 0.01-percent and 0.1-percent solutions; snapdragon chromosomes were doubled with a 0.2-percent solution. The colchicine comes in a powdered form and is easily dissolved in water. It is also advisable to add a wetting or penetrating agent, such as Santomerse, which may be added to the colchicine at about the rate of a few drops to 10 liquid ounces of the colchicine. If you prepare a stock solution of 1-percent colchicine, it is then easy to dilute it to a 0.1-percent or any other concentration up to 1.0-percent. The colchicine solution should be stored in a refrigerator.

THE AUTHOR

S. L. Emsweller, as principal horticulturist in the Bureau of Plant Industry, Soils, and Agricultural Engineering, has been in charge of the investigations on floricultural and ornamental plants since 1935. Before joining the Department he did research at the University of California on various floricultural crops, including the development of rust-resistant varieties of snapdragons. Dr. Emsweller specializes in genetics and cytology, and at present is developing improved types of hardy chrysanthemums and new Easter and garden lilies, including the tetraploid lilies described in this article.