AMONG the herbage crops, cocksfoot (Dactylis glomerata L.)1 and bird's foot trefoil (Lotus corniculatus L.)2 have been shown to be autotetraploids, and lucerne (Medicago sativa L.), having also given segregation ratios which can best be interpreted as tetrasomic, may be regarded as an autotetraploid3. Sainfoin (Onobrychis viciaefolia Scop.) is a tetraploid species with 2n = 28 chromosomes compared with 2n= 14 in O. Caputgalli Lam.4. The question arises whether it is an allo- or an auto-tetraploid. This can best be settled by genetical tests based on the difference between tetrasomic and disomic ratios, but the following observations seem sufficiently indicative to be worth reporting.