NATURAL HYBRIDS BETWEEN ORYZOPSIS AND STIPA. I. ORYZOPSIS HYMENOIDES × STIPA SPECIOSA

Johnson , B. Lennart . (U. California, Los Angeles.) Natural hybrids between Oryzopsis and Stipa. I. Oryzopsis hymenoides × S. speciosa. Amer. Jour. Bot. 47(9): 736–742. Illus. 1960.—Spontaneous, sterile hybrids between Oryzopsis hymenoides and Stipa speciosa heretofore have been referred to O. bloomeri, which species in an earlier paper was shown to consist of a series of hybrids between O. hymenoides and various species of Stipa. On many morphological characters (O. hymenoides × speciosa) is intermediate between its parents and similar to the other hybrids formerly classed as O. bloomeri. It is distinct from the other hybrids on characters which reflect S. speciosa, except with respect to indument of the awn which is recessive. Somatic chromosome counts are: O. enoides, 48; S. speciosa, 64; hybrid, 56. Both parents exhibit regular bivalents at meiosis. The hybrid shows only occasional bivalents and mostly asynchronous splitting or random distribution of univalents at metaphase I. Pollen abortion is complete. No evidence of natural amphiploidy or introgression was found.