Previous research on the interactions of Rhizobium strains with host cultivars has involved the testing of small numbers of plants with a specific strain of Rhizobium in Leonard jar assemblies (Leonard, 1943). The Leonard jar technique in our greenhouse requires frequent watering (up to twice daily) and periodic adjustment of the wick element. We have found the traditional Leonard jar assembly technique inadequate to efficiently accommodate the large plant populations required in plant selection and genetic studies of allelism and linkage.