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A Cyto-Taxonomic Study of an Intergeneric Hybrid Between Oryzopsis hymenoides and Stipa viridula

B. Lennart Johnson and George A. Rogler
American Journal of Botany
Vol. 30, No. 1 (Jan., 1943), pp. 49-56
Stable URL: http://www.jstor.org/stable/2437393
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
A Cyto-Taxonomic Study of an Intergeneric Hybrid Between Oryzopsis hymenoides and Stipa viridula
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Abstract

Natural crossing occurs between Stipa viridula and Oryzopsis hymenoides to produce sterile hybrids. The somatic chromosome number of S. viridula was determined to be eighty-two, and that of O. hymenoides forty-eight. The hybrids showed a somatic number of sixty-five. Great meiotic irregularity was found in the hybrids while normal pairing and separation of chromosomes were found in the parents. For a large number of morphological characters the hybrids were either intermediate between the two parents or else expressed dominance for certain characters of each species. The hybrids had been identified as Oryzopsis Bloomeri, but comparison with the type specimens of O. Bloomeri and O. caduca showed the hybrids to be identical with O. caduca, while they differed in several important characters from O. Bloomeri. Both type specimens were pollen sterile. The geographic ranges of S. viridula and O. hymenoides overlap in the region where the type of O. caduca was collected; but S. viridula does not extend into the region where the type of O. Bloomeri was collected. From this evidence it is concluded that: (1) Oryzopsis caduca Beal is a hybrid between Oryzopsis hymenoides (Roem. and Schult.) Ricker and Stipa viridula Trin. (2) Oryzopsis caduca Beal is distinct from Oryzopsis Bloomeri (Boland.) Ricker. The name and formula, x Stiporyzopsis caduca (Beal) (Oryzopsis hymenoides x Stipa viridula) are applied to the hybrid.

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