It has become quite clear from past studies that the composition and appearance of crystalline inorganic components in plants form an important character index in plant taxonomy. Taxonomic system of Japanese plants of the Saxifragaceae was reexamined from the componental and morphological relation of the crystals contained in the leaves of these plants. Crystal observations were made by the "low-temperature plasma ashing method for biological tissues" that the author had devised. The plants of the Saxifragaceae examined were among those in Ohwi's "Flora of Japan" and comprised 20 genera. Results of this examination are summarized below. Saxifragaceae plants can be divided roughly into three groups from their crystalline components but the majority contain crystals of calcium oxalate[Ca(COO)₂-H₂O]crystals. Therefore, it may be said that the Saxifragaceae plants are a fairly coherent group of plants when looked from their crystalline component. The most interesting fact is that Mitella acerina MAKINO (Japanese name, Momiji-Charumeruso) alone contains calcium carbonate crystals in addition to calcium oxalate crystals. Crystal form in Saxifragaceae plants can be divided into 14 types, and the plants can be classified into 8 groups from interrlationship among these types. Looked from the crystal form, Engler's syllabus classification system, which dose not make a distinction between herbaceous and woody plants, is less of a taxonomical problem than the classification of Hutchinson, Huber, and Takhtajan, which distinguishes the herbaceous and woody plants as different lines. Nevertheless, both classification systems seem to have several problematical points which must fully be discussed in future. The result of the present examinations failed to show any evidence which of these classification systems more closely follows the natural trend, and a concerted and careful conclusion must be drawn after further examination of other characteristics in addition to that of crystalline inorganic components.