Rhus succedanea grows in the warm districts in Japan, and is found in large quantities especially in Kyushu. I have studied the anatomical structure of the leaves of this plant, and especially the distribution of the resin canal. In the leaves of this tree, in each fibro-vascular bundle which has ordinarily a large resin canal in the phloem and which stands as a rule at the inner side of the group of bastfibre, but the developed fibro-vascular bundle has moreover smaller resin canals close by the cambium. These resin canals run parallel to the fibro-vascular bundles in any part, and those fibro-vascular bundles in the lateral veins branch off from those in the common petiole, and those in the veinlet from those of the lateral vein. A great many resin canals are found in the phloem of the common petiole, but in the lateral vein and veinlet there is only one resin canal.
In an adult leaf, resin canals are found in the pith of the pulvinus and are also found in the bigger part of the veins too, but especially there are many resin canals in the pulvinus of the common petiole. In this part the resin canals are found at the periphery and inner part of the pith. Those at the inner part are very few, but at the periphery there are comparatively numerous resin canals, and the cross section sometimes much larger than that of the resin canals in the phloem. The resin canals in the phloem of the common petiole are most numerous at the middle·part of the first internode, and by and by the number diminishes as the internode becomes smaller. The petiole of the leaflets has four relatively large resin canals and any number of smaller ones, but there is only one at the end of the end of the midrib of the leaflets.
In the petiole of the cotyledon, there are only two resin canals, but four in the petiole of the leaflets of the first common leaves of seedlings. All these resin canals enter into the midrib, but their number diminishes gradually, untill only one of them remains at the end of the midrib. While other species of Rhus have a great number of the trichome on their leaves, we can find only a very few of this species, and then only on the cotyledon, : the midrib of the common leaves of seedlings and on the scally leaves of the winter buds of the adult plant.

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四國の内海に面する方面の氣象條件下に於ては、土壤のpHが3.9～4.3迄の所に、第三十六號、第四號、第七號、發十二號、第十七號の試驗地の如き林相を形成した場合に、松茸發生に最もよき地表の氣象條件を附與するものと考へられます。この林相は部分的には少しの差異を認め得るけれどもこれらは一つの性質の林相が變化したものと見る事が出來ます。即ち赤松林が成立して直根の成長衰へ、側根の生長旺盛となり、枝條が繁茂し始むる時期に形成せる林相が第三十六號、第四號、第一號の如く、松の欝閉度相當密、樹冠の下部が地上三～四米の林相の所は土壤のpHは概ね4.0附近であつて松茸發生多く品質良好であり、この状態は林相が第十二、十七號の林相に至る迄、相當長き期間、繼續するものと考へます。從つて、第十二號、十七號は松茸山としての自然的壽命は前三者より短いものと考へます。
次に酸度の低いpH 4.4～4.7の林相を一瞥します。
(イ)松茸の發生が比較的多き所は、どの林相が理想的林相に酷似するか、又は樹冠の最下部が少しく高き所は下木がこれを補つて居ります。
(ロ)發生「中」の個所は理想的林相と性質の異れる林相より出發せるものであつて、土壤的條件に缺くる所ある爲め、松茸發生の森林を形成せる最初の林相より、既に松茸護發生の條件に缺點を有してゐるやうです。
(ハ)發生少き個所は地位よきため、最初に形成せる森林より理想的林相に遠ざかること大となります。
以上の事實よりして、人工栽培は土壞と林相、これに品種を考へる場合に於て成功し、木材生産を主目的とする主旨とは一致し難いけれども、林相を變化せしむる事によつて或る程度まで、その目的を達することが出來ると考へます。

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