Vascularization of Fern Leaves

Abstract

The subject of fern leaf venation is a very old topic and it has been dealt with by many authors during the nineteenth and twentieth centuries. Most of the discussions of fern leaf venation concentrate on its qualitative aspects resulting in descriptions of various types of leaf venation. Considerably less attention has been devoted to the quantitative aspects of fern leaf vascularization. This report will give a brief summary of some of the measurable aspects of the vascular system within the leaves of certain rather common ferns. The collections of the ferns used in this study came from two sources. Those collected out-of-doors came from Giant City State Park or from Jackson Hollow, six miles northeast of Simpson, Illinois. Material was taken with the permission and under the supervision of Dr. Robert H. Mohlenbrock of Southern Illinois University. Other ferns were obtained from the Department of Botany greenhouse at the University of Nebraska. The fern leaves were studied from slides made of cross sections of the material which had been stained with Delafield's hematoxylin and safranin. Whole mounts of cleared leaves or leaflets or parts of these were also studied to obtain vein patterns and angle of branching. All measurements recorded in this study were made by means of an ocular micrometer. All those listed in Table I are averages of many separate measurements. Leaf thickness was measured at veins rather than between veins. Intervascular interval was measured from the vascular tissue of one bundle to the vascular tissue of the next adjacent bundle; thus it includes any specialized parenchyma or bundle sheath cells. Vein width includes only the width of the conductive tissues of a vascular bundle. Angle of branching refers to the branching of vascular bundles from the midvein of the leaf or segment and not to the ultimate branchings in the lamina. It was measured in linear units and the angle 87