Abstract
We observed the morphology of the marine pennate diatom genus Licmophora in Japan using light and scanning electron microscopy, and identified the following four common species: L. californica Grunow, L. communis (Heib. ) Grunow, L. flabellata (Grey. )C. Agardh, and L. paradoxa (Lyngb. ) C. Agardh. They were distinguished from each other by 1) colony structure,2) chloroplast shape,3) shape of valves and frustules,4) winding degree of central rib of valvocopula,5) depth of septum,6) areola shape,7) velum structure,8) number and arrangement of rimoportulae,9) fine structure of head rimoportula,10) number of apical slits and 11) presence of spines. Especially colony structure, areola shape, velum structure and fine structure of the head rimoportula were the most definitive characteristics among the species studied. The fine structure of the head rimoportula is a new distinguishing character revealed in the present study.
