Important informations on detailed and precise morphological studies of tissues，organella and cells of algae are supplied by scanning electron microscopes (SEM) and transmission electron microscopes (TEM) recently，as well as by optical light microscopes (OLM) which have been used for many years.In the present report Undaria pinnatifida was used as a specimen. A comparative study was done using the above three kinds of microscopes in order to know how much degree the surface structure of the organism and solid localization and fine structure of mucilage glands，hair and hair conceptacles，tipical for the alage can be elucidated. As a result，the three-dimensional image obtained with SEM was not so different from that which had been expected，basing on OLM-and TEM-micrographs of cross-section of the algae. However，observation with SEM has advantages of being able to obtain clear image of even ultrastructure and of giving strong impression to eyes on the three-dimensional
difference of surface structure， which is usual1y difficult to detect by OLM or
TEM. It is worthy to mention here that analysis of the image obtained with SEM should be compared throughly with the TEM-micrographs of cross-section，refferring to the OLM-micrographs. Morphology of tissues，organella and cells can be observed finely and precisely by using SEM together with OLM and TEM. Such studies may lead to a discussion not only on the structure but also on the morphology in relation to the function，i. e., on the functional
ultrastructure region.