Micrasterias
Micrasterias is a unicellular green alga of the order Desmidiales. Its species vary in size reaching up to hundreds of microns. "Micrasterias" displays a bilateral symmetry, with two mirror image semi-cells joined by a narrow isthmus containing the nucleus of the organism. This dual semi-cell structure is unique to the group of green algae to which Micrasterias belongs. Each semi-cell contains a single large chloroplast, the site of photosynthesis for "Micrasterias". Chloroplasts within Micrasterias contain chlorophyll a and chlorophyll b and the enzymes required for photosynthesis. The sugar created is used to provide energy for the  organism or, if not used, taken up by many small round pyrenoids which are embedded in the chloroplast. They convert the sugar to a starch for storage. "Micrasterias" can produce both asexually and sexually. Asexual reproduction occurs via mitosis. When this occurs the genetic material of "Micrasterias" is duplicated and two small semi-cells grow between the original semi-cells, gradually increasing in size. Sexual reproduction occurs through a process called conjugation whereby two organisms come together and fuse their haploid cells to form a diploid zygote. This zygote typically forms a thick protective wall which can allow the organism  to remain dormant for many months to survive cold winters and long droughts. When adequate conditions resume, the zygospore will germinate, undergo meiosis, and produce new haploid algal cells. Morphology. "Micrasterias" species consist of two semicells that are almost entirely filled with chloroplasts, with a nucleus that lies at the center where the two semicells are joined together. The gaps between the two semicells are joined by an isthmus. Each semicell is further divided into a polar lobe and two lateral lobes. These lobes can be further subdivided up to the fourth order. As is common in the green algae , the chloroplasts of "Micrasterias" contain pyrenoids. Species. Accepted species. "Micrasterias" comprises the following species: Species names with uncertain taxonomic status. The status of the following species is unresolved: Phylogenetics. Modern molecular phylogenetics suggest the following relationships (not all accepted species are included): Even though "Triploceras" was recovered as embedded within "Micrasterias", there was low statistical support for this placement, so it remains a separate genus.