Abstract
In the previous paper, high correlation between the distribution of oil glands and the percentage yield of essential oil was pointed out. The present study was carried out in 1956 and 1957 in order to see the seasonal fluctuations in both the distribution of oil glands and the percentage yield of oil. P. roseum Willd. (biennial) was used. The results are summarized as follows : 1) The seasonal fluctuation in the distribution of oil glands shows a similar tendency to that of the percentage yield of essential oil, with respect to the position of leaves on the stem (Figs. 1 & 2). The percentage of oil increases gradually from June (spring harvest), reaches a maximum in August (summer harvest) and then decreases somewhatin September. But it increases again in October (autumn harvest), and thereafter decreases remarkably. During the period of a maximum yield in summer, the production of essential oil in young leaves in remarkable. 2) The similar trend in also shown in the percentage of essential oil of fresh plant material, which consists fo leaves and stalks (Table 1). 3) Although the correlation between the number of oil glands and the percentage of essential oil is very high in every season, the regression coefficient is the highest in August and low in October and June (Fig. 3). This suggests that the secretory activity of oil gland reaches a maximum in August. 4) It is concluded that the seasonal fluctuation of the percentage of oil is ascribed to that of both the distribution and the secretory activity of oil gland.
