Based on the dichotomous key, what type of tree did this leaf come from? Horse chestnut
Ginkgo
Honey Locust
Black maple

The very inside of the flower, at the center is the ovary. The ovary extends upwards to become the style and then the stigma on top of that. All three of these structures combined are called the pistil.  Surrounding the style can be one or more filaments each with an anther on the top which contains the pollen. Around all of those structures are the petals, when combined are the corolla. At the base of the corolla, there are green leaves called calyx.directly under the ovary is the peduncle or stem. Please see the attached diagram for more information.