벗풀속 Sagittaria LINN.

1. 잎은 잎자루가 없다   ···························································································································32. 올미

1. 잎은 잎자루가 있다.

2. 잎은 대개 물에 뜨고 장타원형 내지 난상 장타원형이며 수과는 길이 2-3mm이고 암꽃에 짧은 대가 있다 ························ 뜬벗풀

2. 잎은 물 위로 나오고 화살밑형 간혹 장다원형이며 수과는 길이 3~4mm 이다.

3. 잎 열편은 예첨두로서 끝이 실처럼 가늘다.

4. 포복지가 있다.

5. 작은 구경이 달린다 ··················································································································33. 벗풀

5. 구경이 크고 재배한다  ·········································································································34. 소귀나물

4. 포복지가 없다    ·························································································································35. 보풀