The number of spikelets at each node is not important; it may be 1 (as in sect. Roegneria and many of the species that used to be placed in Agropyron) or more than 1 (as in E. viriginicus, E. canadensis, etc.).

For different viewpoints on the circumscription of Elymus, see Assadi and Runemark (1995) (who interpret it to include Thinopyrum and Pseudoroegneria plus many other segregates) or Baum et al. (1991) (who treat Roegneria and Elytrigia as distinct genera). For a revision of the South American taxa, see Seberg and Petersen (1998).

Distribution: Elymus is a cool-temperate genus. It is most abundant in Asia and North America, but extends into Europe, South America, and Australia.

Size: Elymus probably consists of around 200 species. Estimating its size is difficult because its greatest diversity is in Asia, many parts of which are poorly known botanically speaking. An additional complication is a consequence of the differing species interpretations that have been adopted. North American species are thought to have low barriers to interspecific hybridization. Interestingly, this does not seem to be true of Asian species (von Bothmer, pers. comm).

Genomic composition: Elymus is an alloploid genus, all of whose members (so far as is known) possess the St genome in combination with at least one other genome. Most species are tetraploids, but there are many hexaploids and possible some octoploids. All native North American species examined are tetraploids in which the second genome is the H genome. Many Asian species are also tetraploids, but with the Y genome as the additional genome. Other genomes known to occur in Elymus are the P and E genomes.

Table of species: The following table will be built up very slowly (unless funding becomes available). The synonyms listed are those that seem to be in recent or current use and are provided to help in interpretation of the treatment reflected by the first column. Genomic information is provided ONLY if it has been obtained via investigation of the species involved. Reports that do not list voucher specimens made at the time of the genomic investigation are asterisked. They should be repeated, with vouchers being deposited in a herbarium that regularly makes loans available. The species are listed alphabetically for now. The links below will aid in locating names in the first column.

Triticeae