. Bulletin. 1901-13. Agriculture; Agriculture. SIGNIFICANCE OF PABALLELISM IN HEREDITY. 27 a broad-lobed variety included in the same planting. In ,the latter the lower leaves were almost entire, as often occurs in broad-lobed types of cotton. SIGNIFICANCE OF PARALLELISM IN THE STUDY OF HEREDITY. The parallel series of leaf forms of cotton and related plants are of interest in connection with many problems of heredity and breeding. In view of the fact that the same wide range of diversity in leaf forms exists in Gossypium, Hibiscus, and Abelmoschus, it becomes easier to look upon such differen
. Bulletin. 1901-13. Agriculture; Agriculture. SIGNIFICANCE OF PABALLELISM IN HEREDITY. 27 a broad-lobed variety included in the same planting. In ,the latter the lower leaves were almost entire, as often occurs in broad-lobed types of cotton. SIGNIFICANCE OF PARALLELISM IN THE STUDY OF HEREDITY. The parallel series of leaf forms of cotton and related plants are of interest in connection with many problems of heredity and breeding. In view of the fact that the same wide range of diversity in leaf forms exists in Gossypium, Hibiscus, and Abelmoschus, it becomes easier to look upon such differences as within the usual range of variation for this group of plants. Changes of characters to wider or narrower leaves do not require us to believe that a new character has originated or that hybridization with a differ- ent type of cotton has occurred. The theory of hybridization as a cause of diversity of leaf formsis rendered the more unnecessary be- cause the wide range of leaf differ- ences appears not only in the same species or variety, but on the same individual plant. This is well shown in a wild relative of cotton, Ingenhousia triloba, native in Ari- zona. (Fig. 16.) The young plants have entire and broad-lobed leaves, while the leaves of adult plants have long narrow lobes. The branches of Ingenhousia, grown under greenhouse conditions, do not show the same tendency as in cotton to return to simple leaves, but the three-lobed leaves at the base of the branches have very short and broad lobes, quite unlike the tapering long-pointed lobes of subsequent leaves of the same shoot. The upper leaves have five lobes, as in cotton, okra, and Hibiscus carmabinus. The fact that a wide variation in leaf forms occurs on the same individual plants in primitive wild species makes it entirely unneces- 221. Fig. 16.—Plant of Ingenhousia triloba, showing transition from entire to deeply divided leaves. (Reduced.). Please note that these images are extracted from scanned page images
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