Abstract
The results of some experiments at the New York Botanical Garden in 1905 showed that it was possible to introduce foreign substances into the ovaries of the higher plants, in such manner that the egg, or pollen-nuclei, were affected as to their genetic capacity.
Similar results were achieved independently four years later by Major Firth, of the British Royal Army Medical Corps, Dr. Firth being unaware of the previous discoveries.
The removal of my work to the Desert Laboratory in 1906 made it necessary to find new experimental material. Species suitable for the study of the modification of the germ-plasm by external agencies should be genetically simple, and preferably perennial, so that successive generations may be kept alive for comparison, and it is a great advantage if the plant can be brought to maturity in a single season.
Many-seeded ovaries, with the ovules standing in an open chamber, offer the best mechanical features, and naturally, only those which will recover from the traumatic effects of the necessary operations are of value to the experimenter. The above conclusions are based upon a long series of failures of ovaries to mature upon cultures of treated species showing no departures, and upon progenies including notable departures, the parental forms of which proved to be a complex of elementary forms. Satisfactory conditions were finally obtained with a Scrophularia, native to the mountain tops of Arizona. Ovaries treated in 1911 with a solution of one part potassium iodide to 40,000 of distilled water, and the seedlings grown in 1912, included two individuals unlike the parental strain. These and their progeny are unlike their progenitors in the color-pattern of the flowers, the waterrelations of the stems, the degree of differentiation of the tissues, the shape of the wings of the stems, the form and size of the flowers, the growth-correlations and venation of the leaves.
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