Floral Morphology of Chrysothamnus nauseosus speciosus

Abstract

1. Chrysothamnus nauseosus speciosus (Nutt.) Hall & Clements is a potentially important economic shrub of western United States. It is 2-6 feet high, and is a subclimax dominant of the sagebrush-wheatgrass association. 2. It blossoms through September and October. The yellow flower heads are rounded, usually consisting of five disk flowers, with no ray flowers present. 3. The flower bud primordia appear during the latter part of August, and fertilization occurs the early part of October. The floral organs develop in the sequence: corolla, stamens, pappus, and pistil. 4. The marginal cells of the corolla lobes curve inward at an early stage, interlock, and bring about fusion of the lobes. Later the elongation of the stamens forces the flower open. 5. The fibrovascular bundles are equal in number to the corolla lobes but are alternate with their median lines rather than opposite. The stylar bundles are anterio-posterior, and the ovule bundle is lateral. 6. The mature microgametophyte at the time of shedding...