수수꽃다리속 Syringa LINN.

1. 꽃부리통부는 열편보다 짧고 수술은 꽃부리 밖으로 나타난다.

2. 잎은 난형 또는 타원형이다 ········································································································ 103. 개회나무

2. 잎은 피침형이다 ······················································································································ 버들개회나무

1. 꽃부리통부는 열편보다 길고 수술은 밖으로 나타나지 않는다.

3. 꽃차례는 새가지 끝에 달린다 ···································································································· 104. 꽃개회나무

3. 꽃차례는 묵은 가지의 잎집에서 자란다.

4. 잎은 넓은 난형 아심장저이며 꽃밥은 꽃부리통 중앙보다 위쪽에 붙고 가을에는 황색에서 자주색으로 변한다 ···················105. 수수꽃다리

4. 잎은 난형， 아심장저 내지 넓은 예저이며 꽃밥은 후부 바로 밑에 달리고 가을에도 녹색이며 열매에 피목이 뚜렷하다 ············ 서앙수수꽃다리

5. 잎의 뒷면， 잎자루， 어린 가지와 꽃받침에 털이 밀생한다 ···························································106. 털개회나무

5. 잎 뒷면의 엽맥 위 외에는 털이 없다 ························································································107. 섬개회나무