×leydeum

Plants perennial; rhizomatous, sometimes shortly so. Culms to 140 cm tall, 1-3 mm thick. Spikes 10-15 cm long, 5-12 mm wide excluding the awns, erect, sometimes lax, nodes with 2-3 spikelets; internodes 3-5 mm; disarticulation in the rachises, sometimes delayed. Spikelets appressed, with 1-3 florets. Glumes equal or unequal, 10-25 mm long, 0.2-1.5 mm wide, tapering from below midlength or subulate from the base; lemmas glabrous or hairy, awned, awns 1-10 mm; anthers 1.8-3 mm long, 0.1-0.3 mm thick. Caryopses not developed.

Distribution

Oreg.

Discussion

×Leydeum consists of hybrids between Hordeum and Leymus. The number of named ×Leydeum hybrids is substantially lower than that for hybrids between Hordeum and Elymus.

This probably reflects the lower likelihood of such hybrids being formed, because Leymus does not incorporate the H genome of Hordeum, whereas Elymus does. It is also possible that such hybrids are less likely to be recognized, because inland species of Leymus, like Hordeum, have narrow glumes. Of the three species recognized, two involve the coastal species L. mollis, which has flat glumes; these hybrids have intermediate glumes and rachises that tend to disarticulate. ×Leydeum piperi, the only hybrid involving one of the inland species of Leymus, differs from Leymus in its disarticulating rachises, and from Hordeum in having 2 spikelets per node and 2-3 florets in the larger spikelets.

Selected References

Bowden, W.M. 1967. Taxonomy of intergeneric hybrids of the tribe Triticeae from North America. Canad. J. Bot. 45:™11-724

Covas, G. 1949. Taxonomic observations on the North American species of Hordeum. Madrono 9:233-264

Hodgson, H.J. and W.W. Mitchell. 1965. A new Elymordeum hybrid from Alaska. Canad. J. Bot 43:1355-1358

Hulten, E. 1968. Comments on the flora of Alaska and Yukon. Ark. Bot., n.s., 7:1-147.

Lower Taxa

×leydeum dutillyanum, ×leydeum littorale, ×leydeum piperi