and the fronds which are about to . In life, the fronds would have hung vertically whenever the plant was submerged during high tide, and would have flopped over the stipe when the plant was exposed during low tide in a habitus similar to that of the living sea palm. Other specimens from this deposit collected and described by Massalongo in 1855 were actually trace fossils, and they remain assigned to Zoophycos; only the specimens of Z. caput-medusae have been assigned to Postelsiopsis, as those are fossils of the original plant, and not trace fossils. Morphology Postelsia has two distinct morphologies: one for its diploid, monoicous sporophyte stage, which is the dominant portion of the life cycle, and one for its smaller, haploid, dioecious gametophyte stage. Like all seaweeds, the sporophyte stage of Postelsia consists of a thallus, which is made up of a stem-like stipe topped with possibly over 100 leaf-like blades, and rests on a root-like holdfast. The holdfast anchors the organism to the rocks it lives on. The sea palm has no vascular system; the stipe is only for support of the organism and holds the fronds up over other organisms so they can receive more light. The stipe is merely a firm, hollow tube, able to withstand the open air of low tide conditions as well as the crashing waves of high tide. The blades are grooved, with the sporangia held within these grooves. The gametophyte stage is microscopic, consisting of only a few cells. The gametophytes produce sperm and eggs to create new sporophytes. Like all phaeophytes, sea palms use the pigments chlorophyll a, chlorophyll c, fucoxanthin, and carotenes in photosynthesis. Their cell walls are composed of alginate. They use laminarin and mannitol for storage. Life cycle and growth Like most brown algae, Postelsia goes through alternation of generations, and is an annual species. The diploid sporophyte produces, through meiosis, haploid spores, which drip down through the grooves in the blades onto the substrate, which may be mussels, barnacles, or bare rock. These spores develop, through mitosis, into small, multicellular haploid gametophytes, male and female. The male and female gametophytes create sperm and eggs, respectively. The sperm of the male reaches the female egg and fertilizes, resulting in a diploid zygote, which develops into a new sporophyte. Postelsia are green in color as juveniles, and change to a golden brown as they age, reaching a