Botany Of The Cosmos

Day 330: What is "a flower?" Maybe it's not as easy to define as it sounds. Let's take a Cosmos blossom and break it down. Cosmos belong to the family of composites (Asteraceae), a word which might give you a clue that there's more going on here than meets the eye. In the most basic terms, there are two types of "flower" in the makeup of a Cosmos bloom: ray flowers (the "petals") and disk flowers (the "center"). What we commonly refer to as a Cosmos "flower" is in fact a head bearing many small flowers. You can see this in the closeup example, upper right. If you examine the disk through a hand lens, the smaller flowers will become apparent. Depending on the plant species, disk flowers may be a mix of male and female as they are in Cosmos, or male and female flowers may be borne on different heads, in which case they are referred to a "staminate" or "pistillate" depending on the sex. The microscope views show both sexes of Cosmos disk flowers, the brown stamens of the males obvious in the center right image, females lower right. The "birds-and-bees" of botany is quite a complicated process!