ダケカンバ・シラカンバの発芽に関する一実験

抄録

In general, Betula ermani distributes at elevations in mountainous regions higher than that of B. platyphylla var. japonica in Japan. The difference between the distribution areas of these two kinds of birch is considered to be mainly due to the character of germination behaviour of their seeds. Using the seeds collected from the Kitakami Mountain Range in Iwate Pref., the author conducted some experiments on their germination. The materials were kept under three different conditions of I) 0-5℃, wet, 2) 0-5℃, dried and 3) 25-30℃, dried. They were preserved for five different lengths of 5,20,30,60,and 90 days under each condition. The results of the experiments were as follows : 1) Regardless of the condition or length of preservation, the seeds used for these experiments never germinated in the dark, and all of them seemed to be light germination seeds. 2) The minimum length of light exposition necessary for normal germination was two days for Betula platyphylla var. japonica and four days for B. ermani. Seeds preserved under wet condition for a long time germinated by only one treatment of short exposition to light (for ten minutes). 3) The days necessary for starting and finishing the germination were shorter in Betula platyphylla var. japonica than in B. ermani, though the days became shorter inversely to the length of preservation in both species. 4) As the temperature became lower, longer days were required for germination. Seeds preserved under dried condition never germinated in lower temperatures, but the ones preserved under wet condition germinated to a certain extent even under low temperature. 5) According to a preliminary observation, the growth of the seedlings of both species of Betula was promoted by the red part of visible ray.