Vascular System of the Fertile Floret of Anthoxanthum odoratum L.

Abstract

Three collateral bundles occurred in the rachilla of A. odoratum L. at the base of the fertile floret shortly after anthesis. The anterior bundle closer to the insertion of the fertile lemma (bundle 3) produced the trace to its midvein and supplied all of the xylem and some of the phloem for the two stamens and the pistil. One of the pair of bundles on the posterior side of the rachilla (bundle 2) furnished traces to the 2 right laterals of the fertile lemma, and the other (bundle 1) furnished the traces to the 2 left laterals. Either bundle 1 or 2 supplied the trace to the fertile palea. The tracheary elements were contiguous from rachilla bundle to each trace, but sieve elements were consistently contiguous only in the trace to the midvein of the lemma. All of the xylem of bundles 1 and 2 enterd the lemma and palea traces, but the sieve elements and associated intermediary cells combined with those of bundle 3 to form an undulating plexus around the tracheary elements from bundle 3, and the unit rose toward the stamens and pistil. All of the tracheary elements at this level in the rachilla and upward into the pistil were the anomalous ones typical of the xylem discontinuity. From the unified vascular tissue arose, first, a trace to the anterior stamen and, higher, a trace to the posterior stamen. As the insertion of the pistil was reached 4 traces left the rachilla: the large placental bundle of sieve elements and the xylem discontinuity, 2 posterolaterals of sieve elements, and an anterior bundle of sieve elements. The placental bundle supplied the young seed and ended in the bottom of the chalaza with intermediary cells, which blended with those of the chalaza and nucellus.