本文報告土中薺菜種子發芽能力的季節性變遷。在臺灣大學農業試驗場採收薺菜種子，埋於10㎝深土中，每個月取樣，在室內四種溫度下和田間土中進行發芽試驗，凡兩年。掩埋試驗顯示出土的薺菜種子除了掩埋初期以外，皆呈現制約休眠－無休眠的循環；在15/10、20/15、及23/13℃下全年皆有很高的發芽率，在25/20℃之下，發芽率略顯現季節性的波動。種子的無休眠期在晚秋及冬季，夏季為制約休眠期。出土種子在田間的萌芽也集中在冬季及其前後。第二年末期，約有60-75%的種子在土中自行發芽，表示需光性的消失。初步的試驗結果顯示，在台北，薺菜種子自行萌芽主要受到土溫及種子休眠狀態的控制。

The annual change in the germinability of the seeds of shephers's-purse, Capsella bursa-pastoris(L.) Medik, was surveyed by burying the seeds 10 cm under the upland soil surface and exhuming mothly, for two years. The exhumed seeds were then germinated under four different temperature regimes and sown in the outdoor soil. It was found that, except at the beginning of the bural,the seeds showed a conditional dormancy/non-dormancy cycle.Most of the exhumed seeds germinated at 15/20, 20/15,and 23/13.C, irrespective of the exhumed month. While at 25/20.C,the germinability of the exhumed seeds thnded to be seasonal fluctuated. When the seeds were planted in the field at the month of exhuming, seedling emergence occurred only between late autumn and early spring. The buried seeds were thus at non-dormant state around winter and at conditional dormant state during the other seasons. The results suggested that Capsella appear as a winter weed just because the soil temperature falls into a regime suitable to the conditional or non-dormant seeds after late autumn. At the end of the second year, there were 60-75% seeds germinated at the burial, indicating the loss of light requirement.