purplestem aster, red-stemmed aster, swamp aster Symphyotrichum sericeum (Vent.) G.L.Nesom – western silver aster, silky aster Symphyotrichum shortii (Lindl.) G.L.Nesom – Short's aster Symphyotrichum subulatum (Michx.) G.L.Nesom – eastern annual saltmarsh aster Reproduction Ray florets in the Symphyotrichum genus are exclusively female, each having a pistil (with style, stigma, and ovary) but no stamen. Ray florets accept pollen and each can develop a seed, but they produce no pollen. Each ray floret has three petals which are fused together to form a corolla. The floret has one ovary at the bottom, and this ovary contains one ovule. The ovary has an attached style that extends outward from between the ray floret corolla and the rest of the flower head. As the ray floret is blooming, the stigma at the top of the style splits into two lobes to allow pollen to access the ovary. Disk florets in the Symphyotrichum genus are androgynous, each with both male (stamen, anthers, and filaments) and female reproductive parts; thus, a disk floret produces pollen and can develop a seed. The disk floret has five petals, sometimes referred to as lobes, which are fused into its own corolla in the shape of a tube. The male stamen is inside the tube-shaped corolla of the disk floret. It has five anthers, five filaments, and produces pollen. The anthers and filaments are readily visible as separate entities in non-Asteraceae species. Here, they are fused together to form a cylinder, or tube, with their pollen on the inside only. This male anther cylinder surrounds the female style and stigma. As the style is maturing, it elongates up through the anther cylinder, gathering the pollen on its stigma along the way. The ovary is at the bottom of the disk floret style. As with the ray floret, the disk floret stigma has two lobes that are fused together. The disk floret's stigma stays closed while pollen is on it, keeping its ovary safe from self-pollination. After the pollen has been collected and carried off by one or more pollinators, the stigma begins to split into two lobes, opening the style so that the disk floret ovary becomes accessible to receive pollen from another plant. Notes Citations References External links Asteraceae genera Taxa named by Christian Gottfried Daniel Nees von Esenbeck