The systematics of the tube-dwelling diatomNitzschia martianaandNitzschiasectionSpathulatae

摘要

Nitzschia martiana(C. A. Ag.) Van Heurck is a tube-forming diatom of warmer waters. The tubes are rugose externally and contain bundles of long thin cells. The valves bear plain flaps of silica (conopea) externally, which arise near the central raphe system and extend over much of the valve surface; in the light microscope they can be detected as a pair of parallel lines alongside the raphe system. Beneath the conopea the valve arches inwards, so that tube-like canals are formed on the outside of the cell wall. There are no central raphe endings and the fibulae are rib-like. These characters, shown here to be shared byNz.angularisWm. Smith, indicate thatNz.martianashould be transferred into the sectionSpathulataewithin the subgenusNitzschia.