locular (adjective) – containing locules, referring to spores with a cell lumen that is constricted into two or several locules. During spore ontogeny the cell lumen of locular spores is, at least initially, not entirely separated into new cells. Instead endospore swelling(s) constricts the cytoplasm of one single cell into two or several locules. As a result these locules remain connected by a narrow plasma-bridge, referred to as isthmus. Thus, all locules remain part of the same cell lumen for considerable time of the spore ontogeny. Only at the very last stage a narrow endospore septum initiates in the middle of the endospore swelling(s), thus finalizing the process of cell division, separating the locules into newly formed cells. Locular spores are typically found in the Teloschistales; the term is sometimes erroneously applied to spores of the Physciaceae, which, however, have proper septa, i. e., they are mischoblastiomorphic. These spores of the Physciaceae become separated into two distinct cells early during spore ontogeny; each cell with a distinctly separate cell lumen, but not one cell lumen that is subdivided into locules. Related terms: polarilocular, bilocular, plurilocular.