Where the stamens and pistils are found in the same flower it is called perfect or hermaphrodite, as in most of our orchard fruits and garden plants. But when only one sex of these essential organs is found in the same flower it is called imperfect. This with the fruits is often caused by cultivation or crossing, as in the strawberry, where some varieties have perfect and others imperfect flowers. Some of the hybrid grapes and other fruits are practically imperfect. Though they show imperfect stamens, they are not capable of self-pollination. In still other cases the stamens and pistils do not develop together. In some pears, cherries, and plums the pistils are erect and show receptive stigmas while the stamens are yet undeveloped. In such cases cross pollination of varieties is essential to fruitage.