Circinate vernation Term used to describe the protective coiling of young fern leaves into a spiral like a shepherd's crook or bishop's crozier or a fiddle head. . A good, brief review of ferns can be found on the home page of the American Fern Society . A wide range of images of ferns can be seen in the University of Wisconsin's collection . Click here for more fern links . Fern spores are contained in sporangia which are borne on the leaf surface in clusters called sori.
Sori come in all shapes, sizes and locations.
They may appear as dots, dashes or lines on the leaf blade. They may occur tucked under the leaf edge as in the maidenhair ferns or in particular arrays on the leaf surface. A sorus may be protected by an umbrella-like indusium, as shown below. . Spores are contained in sacs called sporangia. In many ferns, a crest of dead cells termed the annulus undergoes hygroscopic movements causing the sporangium to break open exposing the spores to air currents.