Investigations have been conducted by several workers into interspecific hybrids among Pinus densiflora SIEB. et Zucc. (Japanese red pine) and Pinus Thunbergii PARL. (Japanese black pine), but there seems to be many basic problems in morphology yet to be settled. In the present paper, the author attempted to tentatively clasify into five types pure Pinus densiflora, pure Pinus Thunbergii and their hybrids by major external features; (1) Akamatsu (Red pin-e): distinguished as pure red pine by observation of it's needles, winter buds and bark. (2) Ai-akamatsu (Hybrid red pine): recognized as partaking of black pine characteristics by observation of above three external features. (3) Ai-matsu (Hybrid pine): judged as an intermediate type between red pine and black pine. (4) Ai-guromatsu (Hybrid black pine): recognized as the contrary type of (2). (5) Kuromatsu (Black pine): distinguished as pure black pine by the same means. Above distinctions were standardized by macroscopic observation and three characteristics were respectively determined by following points; that is, each of the characteristics of pure red pine is +2, of pure back pine -2, and of intermediate type +1.0, and -1 according to their grades. Then pure races and hybrids are graded by these total points which are figured out by above mentioned methods of marking, as following: (1) +6・・・Red pine (2) (+5)～(+3)・・・Hybrid red pine (3) (+2) ～(-2)・・・Hybrid pine (4) (-3) ～(-5)・・・Hybrid black pine (5) - 6・・・Black pine Sample trees used in this experiment are fifteen in number and they are shown in Table 1. These sample trees grow in the experimental forest (about 0.16 ha.) of Handayama University Forest (the northern part of Okayama city). In the present paper, the relationship between the external characteristics (especially; needle, winterbud and bark) of pure and hybrid pine and the internal structure of their needles are discussed. The microscopic observation on the internal structure of their needles was undertaken to analyze distinctions of tissue, as described in Fig. 1, 2. Considered from the experimental results, it seems most reasonable to conclude that individuals judged as hybrid of Pinus densiflora SIEB. et ZUCC. and P. Thumbergii PARL. by observation of external features may also have the microscopic characteristics in the internal structure of their needles as hybrid of those two species.