Introduction

^{(Photo = Gymoncalycium mihanovichii flower, Mike Keeling)}

When sepals and petals seem alike, or grade into one another, you’ve got tepals.

The Details

Cacti have tepals, which  are petal-like and sepal-like parts. Tepals are the outer parts of a flower, but  the inner tepals look like petals and the outer tepals are where the sepals should be. Usually there is no set number of tepals–a flower might have 40 and the next flower on the same plant might have 43. Other plants have a set number of petals and sepals. For instance, mustard flowers always have four petals and four sepals, no more and no less.

Additional Reading: Flower Parts