A pistil is a distinct organ found at the center of a flower that functions to receive pollen and produce seeds or fruit.
Pistils: a botanical perspective
The essential unit of the cannabis reproductive organ is the pistil. Not all plants have pistils as part of their female reproductive organ (i.e. the gynoecium), but it is one of the possible divisions and subdivisions a plant can have. Not all plants have pistils, and in these cases they may directly divide their gynoecium into one or many carpels, which is the smallest unit responsible for making female sex cells.
Generally speaking, a single pistil may contain one or many carpels fused together. The carpel is responsible for producing female sex cells which will go on to become seeds. In all plants, including cannabis, each carpel is then composed of three structures: a stigma, a style, and an ovary. The stigma is a sticky tip at the end of each style which collects pollen. The style, a long stalk connected to the stigma, transfers pollen to the ovary which is located at its base. The ovary is composed of one or more ovules which produce egg cells. These egg cells become fertilized by the pollen delivered from the stigma. The fertilized egg cells then become seeds or fruit. The pistil encloses and delimits these structures.
Pistils and their associated reproductive structures are the general hallmark of most female vegetation; however, there is much diversity. The pistils and surrounding anatomy of cannabis have been a point of contention among botanists over the last century. Initial dissections led scientists to believe the flower of a female cannabis plant was composed of one carpel and one ovary, which is supported by the observation that each bract (which contains the carpels) makes one seed. Although two stigmas were present during this dissection, indicating two carpels, a second “carpel-like” structure was thought to be posterior thickening from the formation of a placenta.
It was not until histological studies were later conducted that a widely accepted theory emerged. This theory proposes that female cannabis flowers do in fact contain two carpels, but they are fused as one. This fusion results in one ovarian chamber at their base.
Pistil vs. stigma
The cannabis community uses the word pistillate to refer to female cannabis plants, which are more economically valuable as they produce colas with buds full of cannabinoids. When a cannabis plant just begins to flower, it exhibits white hair-like structures on its buds, which are often incorrectly referred to as pistils, but are in fact stigmas. Stigmas make up part of the pistil, the only visible part since the rest is covered by a small leaf called the bract.