The author, who, for some years past, has been studying from several angles and in quantitative way the relation between plants and their surrounding conditions, has been able to deduce from time to time some results, which are of some significance from the view-point of forest ecology and which may help support the conception of so-called phytometer. The subject-matter of ecology, the interrelation of plants with their surrounding conditions, naturally require very careful treatment and is one perhaps that can only be approached with power of inventive conception. To meet such a requirement, very close observation and ample experiments based on exact measurements, such as we now see carried on in the fields of morphology and physiology may be essential. Just such quantit a tive studies in ecology are now being fast introduced into the field of forestry, thus giving ride to the conception of plant-indicators or phytometers. The conception of plant-indicators or phytometers is really one of wide application, and almost any feature of plant life may be regarded as admitting such conception. However, such feature as the variation in histological structure and also of physiological process of plant, as it may easily admit of quantitative treatment, may have the great likelihood of well developing such conception. Among some new facts of plant life which the author in his study has been able to observe and which may be found useful as phytometer, the value set to wavyness in the lateral walls of epidermal cells in the leaves of some special plants as Taraxacum albidum and the ratio of the value of absorption to that of transpiration may stand somewhat prominent. The author fully believes that such quantitative studies as he has carried on will go to add to the practical value of phytometer used in the field of forest ecology.植物生態學上に於て取扱ふ環境は純正植物生理學の取扱ふ環境に比し, 一層複雜であつて, その取扱ひに特別なる考慮考察を要する場合が多いことはすでに述べた如くであるが, その生態學的環境を正しく認識するためには植物と外界との相互關係を數量的に仔細に觀察することが第一に必要である。例へば SCHIMPER (76) が提出せる生理的乾燥なる概念は生理及び生態學的方面に於ける大なる警鐘ではあつたが, 自然界の實際的現象に於て果してどれ丈けその概念があてはまるかに就いては多くの疑問があつた。すでに HUBER (25), STOCKER (82, 83, 84) の詳細なる實驗的研究によつて, 泥炭濕地及び鹽性濕地の植物が生理的に決して乾燥状態にあるものでないことを明かにせるが如きは, 生態學的環境を理解するに當つて實驗的觀察の如何に重要なるかを雄辯に物語るものであらう。かくの如き研究的用意は一般農林學殊に造林學方面に於て植物生育地の環境を論ずる場合に當然準備さるべきもので, 特に指標植物或は Phytometer 等の利用を考慮に入れる場合に於ては, あらかじめ充分なる實驗的數量的根據による研究を必要とすることは勿論である
