Mutations, Variations, and Relationships of the Oenotheras

Mutations, Variations, and Relationships of the Oenotheras

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Mutations, Variations, and Relationships of the Oenotheras

Mutations, Variations, and Relationships of the Oenotheras

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Excerpt

By D. T. MACDOUGAL, A. M. VAIL, AND G. H. SHULL.

SCOPE OF INVESTIGATION.

The oenotheras have furnished so much evidence of importance in connection with saltatory action in heredity that it has been deemed important to continue the cultural investigation of the group begun in 1902.

Seeds representing the species in cultivation in the principal botanical gardens of the world have been procured, and these, in addition to a large number of forms native to eastern North America, have been grown in guarded cultures.

Attention has been paid to the occurrence of mutants in Oenothera lamarckiana with a view to testing the coefficient of mutability and the influence of environmental conditions on mutation. Extensive sowings have been made for the purpose of finding derivatives hitherto undetected, with a coefficient of mutability so small as to have escaped observation. Descriptions of known mutants have been made independently for the purpose of comparison with supposedly identical forms in Amsterdam and of facilitating observations of all kinds upon the subject.

Many important relations between mutants and their parents may be most advantageously considered by statistical methods, and the studies begun by one of the authors in 1904 have been continued and extended to include additional mutants. The height and branching of the stems and the width and length of the leaves have been again taken into account, but owing to the great susceptibility of these organs to variation in direct response to environment, measurements have also been made upon the buds. The lesser variation of the latter in correlation with vegetative characters makes them much more satisfactory for the study of hereditary relations, and it is clear that their statistical study in connection with pedigree-cultures will demonstrate in several generations the permanence or evanescence of the mutant types and give decisive answers to such questions as the relation between fluctuation and mutation and the "fixing" of variations through self-fertilizations or their disappearance through crossings.

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