Plant reproductive morphology is asexual, producing only spores. Similarly, flowers produced by the sporophyte may be described as "unisexual" or "bisexual", meaning that they give rise to either one sex of gametophyte or both sexes of gametophyte. The flower is the characteristic structure concerned with sexual reproduction in flowering plants (angiosperms). Flowers vary enormously in their construction (morphology). A "complete" flower, like that of "Ranunculus glaberrimus" shown in the figure, has a calyx of outer sepals and a corolla of inner petals. The sepals and petals together form the perianth. Next inwards there are numerous stamens, which produce pollen grains, each containing a
Polygonum ramosissimum calyx. The calyx is around long and 5-parted with the outer three sepals longer than the inner sepals. The seeds are produced in fruits called achenes, which are egg-shaped, dark brown and around long. The achenes also have a smooth shiny surface. The late season achenes are larger, from 4 to 15 mm long. There are a number of forms and two subspecies, that vary in flower and foliage coloration. "Polygonum ramosissimum" has great morphological variability, which is notable on the same plant, between flowers and fruits produced early in the blooming season verses those produced late in the season,