The epidermis of the ovules forms the much elongated cells, known as the Malpighian cells of the seed coat. The outer walls of the Malpighian cells are much thickened and are composed of layers differing in physical properties. One of these layers is the light line which in most seeds is impervious to water until it is modified by weathering or by some artificial means. The light line is apparently only more compact cellulose for it hydrates quickly in water at 80° C. and then gives a distinct cellulose reaction and is permeable to water. The action of the weather on seeds lying out over winter is to open the line and thus permit the embryos of the seeds to obtain water.
Proceedings of the Iowa Academy of Science
©1922 Iowa Academy of Science, Inc.
Martin, J. N.
"The Structure and Development of the Seed Coat and Cause of Delayed Germination in Mellilotus alba,"
Proceedings of the Iowa Academy of Science, 29(1), 345-346.
Available at: https://scholarworks.uni.edu/pias/vol29/iss1/69