Floral Morphology of Arceuthobium americanum

Abstract

Male flower 1. The male flower is thought to be originally tetramerous. 2. The anther, although unilocular, is found to be characterized by a system of sterile tissue which represents what is left of the separating partitions of a tetrasporangiate anther. 3. The haploid chromosome number is 14. Female flower 4. The ovary wall is made up, not of two fertile but of four sterile carpels. These are diagonally arranged and show varying degrees of fusion. 5. The two embryo sacs in the central papilla lie in the orthogonal plane, and therefore must be borne on an inner alternating whorl of orthogonally arranged carpel rudiments. This inner whorl bears not two but four archesporia, only one pair forming embryo sacs. The structure of the gynoecium must therefore be represented as G = 4 + 4 and not as G = 2. 6. The archesporia are not unicellular but multicellular. 7. The gynoecium of the one genus of the Santalaceae examined resembled Arceuthobium in being composed of two alternating whorls of carpels.