 Fruit Triumph of the Angiosperms Flowers, the evolutionary newcomer in the plant kingdom, begin to change after the ovules in the ovary are fertilized. Almost as soon as pollen tubes grow down the style towards the ovary, the stigma of the flower begins to synthesize the hormone ethylene, which triggers aging of flower parts, not essential in seed and fruit formation. In many flowers it is the ovary wall that grow rapidly to surround and protect the growing seeds, embryos for the next generation. In other flowers it is mostly the receptacle that grows to surround the seeds. Other flowers provide no fleshy part around the seeds. Ovary walls that develop into walls of the fruit include three layers collectively called the paracarp. The skin of the fruit is the exocarp, the fleshy middle is the mesocarp, and the inner layer with the seeds is the endocarp. Botanists classify fruit according to one, whether they are fleshy or dry, and two, how they develop from flower parts. The layers of the paracarp and dry fruit are often fused into one layer. Fleshy fruits can be simple or complex. Simple fleshy fruits develop from one or more carpals, which are united. While complex fleshy fruit developed from separate carpals, simple fruits. Droop fruits are fleshy with a hard pit. These fruits have one or more carpals with a single seed in each carpal. Berry fruits are fleshy and have one or more carpals with many seeds in each carpal. And poma fruits can develop from the ovaries but mostly from the receptacles. Carpal walls become hard cores. Complex fruit is fleshy fruit developed from multiple carpals. Aggregate fruits developed from one flower with multiple carpals. Multiple fruits developed from the fusion of tightly packed flowers that have ovaries that fuse as the fruit develops. Other fruit are dry where the paracarp is fused into one layer. Dehescent fruit split along seams and release seeds when they mature. Indehescent fruit remains around the seeds when they mature. Paracarp stays hard and thin. So even though we have common names for some of the fruits in this learning activity, such as calling squash, tomatoes, beans, and peapods vegetables, while calling acorns and pecans nuts, they are all anatomically fruit of the plant. Enjoy and eat a variety of fruits. They're good for you.