0023-6152

AA00247166

22553

Unrefereed

So far as the natural system of classification of the species of the genus Pinus is of concerned, it is most complete and we have a wide literatures on this subject. We believe that the natural system of classification of the genus Pinus was systematized perfectly in A, ENGLER and K. PRANTL's "Die natürlichen Pflanzenfamilien 2-Auflage, 13-Band" published in 1926 (3). This represented a long step forward as compared with either their first edition (1889) or A. ENGLER and E. GILG's "Syllabus der Pflanzenfamilien 9 und 10-Aufrage (1924)," and especially it takes into consideration the anatomical characters of the leaves as the basis of classification as KOEHNE (5), MASIER (10) and SHAW (14) had already attempted to do. We, therefore, considered what elements of the anatomical characters of the pine leaves would be most important to the new natural system of classification of A. ENGLER and K. PRANTL (3). And beginning with those elements which have the closest connection with a natural system of classification, and proceeding to those of less vital relation, we have worked to establish a practical artificial system of classification of the genus Pinus, which shall correspond as closed as possible to the natural system of classification. The anatomical characters of the leaves used for this purpose show in each species some one definite peculiarity and these characters, such as are indicated below, are easily distinguishable in a transverse section of a leaf:- 1. Whether the fibro-vascular bundle is single or double 2. Are there in the stelar tissue surrounding the fibro-vascular bundle the sclerenchyma strengthing cells, which show the chemical reaction of hypoderm cells? If so, what degree of development do they show? 3. The shape of the endoderm. 4. (a). Are the walls of the endoderm-cells uniform or otherwise? (b). Are the outer walls thick, or not? (c). Are there both thick and thin outer walled cells? 5. Are the endoderm-cells of equal, or very unequal size, some of them large? 6. The position, number and sometimes the size of the resin canals. 7. Are the cells which surround the resin canal thin or thick walled? 8. When resin canais are situated close to the hypoderm, do the sclerenchyma cells, which encircle the resin canal, surround it perfectly on all its circumference? Are they wanting in the part touching the hypoderm? 9. The degree of development of the hypoderm. 10. The thickness of the epiderm, and the situation, sometimes the number of the stomata. But it must be considered as an inevitable consequence of the artificial classification that there are a few points inconsistent with the natural system of classification (3). For the arrangement of Subgenus, Section and Subsection etc. of the natural system of classification we are indebted to A. ENGLER and K. PRANTL(3), but in regard to the scientific names, there are not a few we owe to other botanists. Since the anatomical characters formed in a transverse section taken from the middle part of leaf shows most clearly the characteristic structure of a given species (12, 15), the spacies were distinguished on the basis of such transverse sections. In the case of species for which green leaves were not available, a section of about 2 cm. in length was cut from the middle part of withered leaves of dried specimens. And after expelling the air from the dried leaves by boiling, they were put to soak in a mixture of equal parts of glycerin and aether for from 6 months to one year, after which the leaves became normally expanded. Then they were made into transverse sections for the examination. Concerning the number of the species of the genus Pinus the botanists have many different opinions. A. ENGLER and K. PRANTL (3) say there are 80-90 species. However, while accepting the conclusions of other students, we have made some corrections in the species. T. DOI collected the leaves of most of the species of the genus Pinus. K. MORIKAWA has been collecting the leaves of the remaining species and has made a comparative examination of the anatomical characters of various kind of leaves and has distinguished all species as much as possible. We must be very much obliged to Prof. Dr. R. KANEHIRA, Prof. Dr. M. FUJIOKA of the Department of Agriculture of Tokyo University, and Prof. Dr. S. KAWAGOE of the Agricultural and Forestry College Kagoshima for their useful books of reference and precious materials.