The approach in this study to discover more about the relation between growth rate and adaptation to particular sites was an examination of the quantitative differences in growth, soluble carbohydrate and amino acid content in the four experimental species: Lolium perenne (S24 strain), Dactylis glomerata (S143 strain), Festuca rubra, and Agrostis tenuis. On the basis of the growth studies, the species cloud be seen to differ and form two groups: I. perenne and D. glomerata in one group, and A. tenuis and F. rubra in the other. When complete nutrient solutions were supplied to these species in treatments of increasing concentration the two groups were seen to differ in the pattern of response of their soluble carbohydrates. When the treatments used in further experiments differed only in nitrate, ammonium, nitrate/ammonium proportions and phosphate at different nitrate concentration, definite treatment effects were found in each species, and in many cases, the response of the species could be seen to be significantly different. Further, in many cases, the differences divided the species into the same two groups observed in the growth experiments. However, when the effects of the separate ions were examined, these species differences appeared to be due mainly to quantitative differences rather than to differences in pattern of response. The examination of amino acid content of the species did not appear to clarify the differences observed between the species, though this examination did explain some of the fluctuations of soluble sugar content which could in some cases be related to the yields and rates of growth in the species.