Fully fertile and has 96 somatic chromosomes. True breeding for morphological appearance and herbage odor M. arvensis, a standard tester strain used in all interspecific hybridizations. The origin of this strain is unknown. We reported the strain as being of European origin since it was part of a collection from Europe. However, J.K. Morton, Univ. of Waterloo, Waterloo, Ont. is quite certain from calyx morphology that it is from North America. Strain is fully fertile and has 96 somati chromosomes as determined by Ikeda (1961). Very susceptible to verticillium wilt and powdery mildew. The strain is true breeding for phorphological appearance and herbage odor. The herbage odor is apparently equivilent to pure isomenthone, but chemical assay of the oil has not been completed. This may be isopulegone rather than isomenthone.