Algal anatomy

cardinal organ part of lower plants that is the region at the distal end of either a peduncle or a pedicel where the floral appendages (e.g.: sepals, petals, stamens and pistils) are attached

thumb|upright=1.3|Scanning electron micrographs of frustules from some algae species - scale bar = 10 micrometres in a, c and d and 20 micrometres in b A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on diatoms as pectin, a fiber most commonly found in cell walls of plants. This layer is actually composed of several types of polysaccharides.

thumb|Germinating Resting-Gonidia: A (appears as "4") is of Ustilago receptaculorum; B is of [[Tilletia Caries. sp denotes the gonidium; pm, the promycelium; and d, the sporidia: in B the sporidia have coalesced in pairs at v.]] A gonidium (plural gonidia) is an asexual reproductive cell or group of cells, especially in algae.

thumb|right|Schematic drawing of Cafeteria roenbergensis ([[Heterokonta: Bicosoecida) with two unequal (heterokont) flagella: an anterior straminipilous (with tubular tripartite mastigonemes) and a posterior smooth]] thumb|right|A chrysomonad (Heterokonta: [[Chrysophyceae) under TEM, with a smooth flagellum (1) and a long flagellum covered with mastigonemes (3)]] thumb|Two cryptomonads (Cryptophyceae) under SEM. Mastigonemes not visible.

thumb|300px|Conceptacle of Fucus thumb|300px|Cystocarp of Amphiplexia hymenocladioides Conceptacles are specialized cavities of marine and freshwater algae that contain the reproductive organs. They are situated in the receptacle and open by a small ostiole. Conceptacles are present in Corallinaceae, and Hildenbrandiales, as well as the brown Fucales. In the Fucales there is no haploid phase in the reproductive cycle and therefore no alternation of generations. The thallus is a sporophyte. The diploid plants produce male (antheridia) and female (oogonia) gametangia by meiosis. The gametes are