Laboratory analysis and tests of seed samples were originally undertaken by governmental agencies in the United States and other countries to inform farmers concerning the weed seed content and plant producing capacity of seed lots. The determination of seed purity and the detection of seeds of noxious weeds have not proved difficult provided that representative samples of seed are submitted. Illustrations of weed seeds in bulletins and books, together with the use of herbarium specimens, have made it possible' to identify with some degree of certainty foreign seeds found in crop seeds. Efforts to measure the plant producing capacity of seed lots have been less successful than to identify weed and crop seeds, because of (a) a lack of knowledge as to the factors affecting the viability and germination of many kinds of seeds, (b) difficulty of interpreting what constitutes normal germination and (c) inability to interpret the value of impermeable legume seeds in obtaining and maintaining field stands.