ABSTRACT
Moreover, a fundamental difference exists between the functions of anatropy and orthotropy on the one hand, and campylotropy on the other. The anatropous ovule is widespread among angiosperms. According to Davis (1966), 204 of the 315 families are exclusively anatropous. Most probably anatropy is the original type of ovule in angiosperms. By the anatropous curvature the micropyle is brought near the placenta, thus shortening the pathway for the pollen tube. Orthotropy is found in 20 angiospermous families and is often associated with mono-ovulate pistils with a single, erect ovule, the micropyle directed towards, or even contacting the stylar transmitting tissue (e.g. Piperaceae, Polygonaceae, Myricaceae, Juglandaceae, Urticaceae and Zosteraceae).
