1. From 4 n×2 n and reciprocal crosses within Dactylis glomerata subsp. lusitanica and D.g. subsp. smithii and between these two subspecies, two triploids, two polyhaploids and a 3n+1 plant were obtained. The two subspecies differ considerably as regards the extent of crossability with respect to intrasubspecific 2n×4n and recriprocal crosses. 2. The cytology of the triploid Dg(1 x sm) 933-III-6 and the 3n+1 plant Dgl 936-I-6 was studied. Chiasma frequency and multivalent frequency per chromosome for these two plants was compared. The frequency distribution for trivalents in the Dg (1 x sm) 933-III-6 plant was compared with the expected binomial distribution. There was a good fit. Data show no evidence for structural differentiation between the two subspecies. 3. In the triploid plant, at anaphase I the distribution of chromosomes did not deviate significantly from a binomial distribution. 4. The triploid and 3n+1 plant had nearly 28% pollen fertility. The 3n+1 plant had significantly higher variance for pollen grain size than the diploid lusitanica plant. 5. From crosses of an asynaptic plant with a normal diploid a primary trisomic plant was obtained. Cytology of the trisomic was studied. In nearly half of the PMCs a trivalent was formed.