ISSN 1188-603X

No. 199 July 26, Victoria, B.C.
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2


From: Mary Barkworth []

AEGILOPS and TRITICUM: These will be treated as separate genera in the Manual of Grasses for the Continental United States and Canada (henceforth the Manual). They are morphologically and ecologically distinct but the cytological and evolutionary arguments for treating them as a single genus are extremely strong.

AGROPYRON: One of the relatively few points of agreement in the perennial Hordeae is that Agropyron should be restricted to the crested wheatgrasses. The problems left are a) what to do with the ex-Agropyrons and b) to determine which taxa are present in North America. The treatment I have used before, in which three "species" are recognized, is artificial.

DASYPYRUM: A well accepted annual genus that is known in North America only from a historical collection of Dasypyrum villosum that was made in Pennsylvania.

ELYMUS: This I interpret as including Sitanion, Roegneria, Elytrigia, and Hystrix as well as several species that used to be in Agropyron. SITANION is a North American taxon. It is, I agree, morphologically distinctive, but it hybridizes readily with species of Elymus. This last does not preclude it being recognized as a genus, but I have not done so in the Manual treatment. ROEGNERIA is accepted by Baum and most Chinese taxonomists, but it is even harder to distinguish from the bulk of Elymus than Thinopyrum. Baum et al. (1991) transferred some North American species to Roegneria but, in my opinion, they do not belong in that taxon, no matter at what level it is recognized. ELYTRIGIA: The type species of Elytrigia is E. repens. It looks, in overall habit, very like other species of Elymus, but was kept in a separate genus partly because of its strongly rhizomatous habit and partly because it hybridizes with other species that I include in Thinopyrum but others included in Elytrigia. HYSTRIX: This taxon presents a problem. There is reasonable evidence that its type species belongs in Elymus, but there is also evidence suggesting that Hystrix californica is more closely related to Leymus than Elymus. For now, I include H. californica in Elymus with which it agrees in overall habit and habitat preference. EX-AGROPYRONS: Some of the other species that have been transferred from Agropyron to Elymus are Agropyron trachycaulus (= Elymus trachycaulus), Agropyron boreale (= Elymus alaskanus), and Agropyron dasystachyum (= Elymus lanceolatus).

EREMOPYRUM: A well-accepted annual genus of which one species, Eremopyrum triticeum, is fairly common in North America. It looks like an annual crested wheatgrass and grows in disturbed sites.

HORDEUM: This will be treated in its traditional sense.

LEYMUS: This genus consists of several alkaline tolerant species. Its members fall into two morphologically distinct groups, one shoreline and primarily coastal, the other inland and non-shoreline. At one time, it was believed to consist of allopolyploids that combined the genome in Psathyrostachys with that found in Thinopyrum. More careful checking revealed that there is no evidence for presence of the Thinopyrum genome in Leymus.

PASCOPYRUM: A monotypic octoploid genus whose only species, P. smithii, is an alloploid derivative of Elymus and Leymus. It is often misidentified, either as Elymus lanceolatus or as Leymus triticoides.

PSATHYROSTACHYS: A Eurasian genus of approximately 22 species. It is generally accepted by Eurasian taxonomists. The only species in North America, P. juncea looks very like Leymus cinereus, differing chiefly in having tidier looking spikes. Yes, that is how I think of it. I am told that the other species are quite distinct from Leymus, but the two genera share at least one genome.

PSEUDOROEGNERIA: A genus of approximately 20 species, only one of which occurs in North America, P. spicata. I am assured by those that know the other species in their natural habitat that the genus is morphologically and ecologically distinct from Elymus. The native species differs from Elymus in its skinnier culms and leaves.

SECALE: An exceptional genus in the Hordeae being a Linnaean genus about whose generic limits there is no argument. It has two species but only Secale cereale is known to be established in North America.

TAENIATHERUM: Like most annual genera (Aegilops and Triticum are notable exceptions), Taeniatherum has been widely accepted. Its only species, Taeniatherum caput-medusae, used to be included in Elymus.

THINOPYRUM: One of the more controversial genera in the tribe. The representatives that I know have distinctive, thick, inflexible glumes that are truncate, obtuse,or acute, trullate spikelets, and florets that are slow to disarticulate. Two species are common in North America, T. ponticum (the old Agropyron elongatum as interpreted by A.S. Hitchcock) and T. intermedium.

Postscript: The treatment of many North American species also needs considerable further study. The fact that one or two accessions of a species form fertile hybrids on an experimental farm does not guarantee that such hybrids form naturally, nor that, if they do so, that they are capable of becoming established. There is also a need to obtain experimental information on how much phenotypic plasticity is present in a population. Such plasticity, particularly in predominantly selfing species, could lead to the formation of morphologically distinct entities of little taxonomic significance.


Abbreviated from a posting on TAXACOM discussion list.

Formal registration of plant names is a new concept which will be voted on at the Nomenclature Session of the next International Botanical Congress, St. Louis, 1999. [See BEN # 185, Feb. 28, 1998]

Botanists in the Research Division of the Missouri Botanical Garden have carefully studied the arguments and mechanism for registration, as published and demonstrated to date (see They are almost unanimous in opposing it for two fundamental reasons:

  1. The botanical community would for the first time depend on the authority of a single organization (the International Association of Plant Taxonomist - IAPT) for the valid publication of names, in contrast to the present practice of independent and unencumbered publication in a book or journal.

  2. Registration would not usefully and significantly add to the nomenclatural information already available; instead it would duplicate or replace effective systems.

In addition, the Missouri botanists see serious problems in the mechanism for registration that seem not to have been addressed. They urge all IAPT members and institutes to study the information presented, and then weigh the pros and cons before voting on registration at the St. Louis Congress.

The full text of this discussion paper is available at:

In the discussion triggered by this position paper, Dr. Joseph Laferriere [] asked:

"Under the registration proposal as currently envisioned, how can a reader tell from looking at a newly published name in a journal whether or not it has been registered? Under the current system, I can tell within 30 seconds whether or not a new name has been validly published." "Under the registration proposal, as I understand it, I now have to ask whether the editors fulfilled the registration requirements."


From: Adolf Ceska []

Aiken, S.G., M.J. Dallwitz, C.L. McJannet, & L.L. Consaul. 1997.
Fescue grasses of North America. Canadian Museum of Nature, Ottawa. CD-ROM (runs under MS-WINDOWS 3.1, 95, or NT).

Available from:
Publications Department, Canadian Museum of Nature, P.O.Box 3443, Station D, Ottawa, Ontario, Canada K1P 6P4 Phone (613) 566-4292, 1-800-263-4433 (Canada & U.S.A.); FAX (613) 566-4763; e-mail:

Please inquire about the price; I heard it's minimal, just to cover handling and shipping ( < CDN$10.00).

This CD-ROM contains a taxonomic monograph of 46 species and subspecific taxa of North American fescues. The species treatment gives details on the type specimen, synonymy, morphological description, habitat, distribution, chromosome numbers, and miscellaneous comments. There are more than 200 images linked with the descriptions.

The information is based on 16 years of research on the genus Festuca and is maintained at the Canadian Museum of Nature in a DELTA data base. The interactive identification and information retrieval package, which is an integral part of the DELTA system provides an easy access to the information and offers a powerful method of interactive identification (INTKEY).

This is a truly remarkable work. I would like to thank

  1. Dr. Susan Aiken and her colleagues for their taxonomical work,
  2. Dr. Dallwitz and the DELTA team for releasing the INTKEY program for the use with with this package, and
  3. the Canadian Museum of Nature for producing this CD-ROM.

If you don't have the CD-ROM drive, visit this web site: That site contains almost the same information that is on the CD-ROM. For more information on the Festuca DELTA set see: Aiken, S. et al. 1997. Canadian Journal of Botany 75: 1527-1555.

What about other CD-ROM sets? The Canadian Museum of Nature produced a set on the saxifrages of the Canadian Arctic - I have not seen that one. I know, however, that Dr. George Argus has a sophisticated DELTA set of North American willows. Would it be possible to produce a similar CD-ROM with his treatment of North American willows?

Submissions, subscriptions, etc.:
BEN is archived at