A method for the collection and analysis of free amino acids in very small quantities of nectar is described. By dansylation and three-system polyamide chromatography individual amino acids may be detected at concentrations as low as 10 pmoles per μl. This has been used for the identification of constellations of acids present in floral nectar from species and hybrids of Aloë, Oxalis, Silene, Cercidium and Armeria. Almost without exception, nectars of F1 hybrids contain all of the amino acids found in the nectars of both parents combined. The usefulness of this‘additiveness’in tracing the phylogeny of groups of species in which allopolyploidy and auto-polyploidy may have played a role is illustrated by analyses of nectars from species of Geranium (section Ruberta). Also the value of nectar amino acid analyses in the investigation of intro-gressive hybridization is illustrated by studies of Aquilegia and Penstemon in the Sierra Nevada of California. The constancy of the amino acid patterns in parental species contrasts with the recombination patterns in the hybrid swarms. Finally, it is suggested that nectar amino acid patterns are as useful chemotaxonomically as other groups of plant chemicals and should be utilized accordingly.