以兩種鬼針屬(Bidens)植物(咸豐草(Bidens pilosa L.)及大花咸豐草(Bidens pilosa L. var. radiata Sch.)之種子為材料，於1999年7月兩種鬼針草屬植物開花時，在花梗上分別掛上1-15天標籤，以後每天採集種子(瘦果)，行乾燥處理後並分別稱重及量其長度、寬度，後行種子之發芽能力檢定。以探討開花後不同天數之種子重量及發芽能力之關係。試驗結果如下：1. 兩種鬼針屬植物種子在開花後第10天後種子重量即不再增加，而咸豐草種子百粒重較大花咸豐草種子百粒重為重，長度在兩種鬼針屬植物差異並不大，而寬度則咸豐草種子較大花咸豐草為寬。2. 開花後1-15天種子之發芽能力，咸豐草種子於開花後6天、大花咸豐草種子於開花後5天，就具備發芽能力。而發芽率、發芽速率在兩種鬼針屬植物間隨著開花後天數之增加而增加，平均發芽日數則隨開花後具備發芽能力起隨開花天數之增加，平均發芽日數有縮短之現象。3. 開花後1-15天種子之重量大小與發芽能力之相關而言：兩種鬼針屬植物除平均發芽日數與各性狀間呈顯著、極顯著或不顯著之負相關外，其餘各性狀(百粒重、長度、寬度、發芽率及發芽速率)間皆呈顯著與極顯著之正相關。

Two species of Bidens, B.pilosa L. and B.pilosa L. var. padiata Sch. were used to study the relation between seed weight and germination ability. After flowering, on July 1999, the flower stalk of two species of Bidens were labeled separately every day . The seeds ( achene) were collected with 1-15 days intervals. After drying, the weight, length and width of sees were measured, and the germination ability was tested. 1.The seed weights were not increased ten days after flowering in two species of Bidens. B.pilosa L. had greater in 100-seed weight than that of B. pilosa L. var. raditata Sch. The difference of length was not significant between two species of Bidens, but B. pilosa L. was wider in seed width than B. pilosa L. var. radiata Sch. 2.B.pilosa L. had the germination ability six days after flowering, and it was five days after flowering in Bidens pilosa L. var. radiata Sch. The more the days after flowering, the more germination percentage and speed of germination in two species of Bidens. It was found reversed in mean days to germination. 3.Except mean days to germination, correlations between characters ( 100-seed weight, seed leanth, seed width, germination percentage, and sped of germination)were positively correlated.