|BOTANICAL ELECTRONIC NEWS|
|No. 197 July 11, firstname.lastname@example.org Victoria, B.C.|
On several occasions, Adolf has asked me to provide an overview of the generic treatment of the Triticeae (= Hordeae) as it will appear in the Manual of Grasses for the Continental United States and Canada. In the past, I have pleaded lack of time but this weekend I agreed to trade favors. What follows is an introduction (BEN # 197), a key to the genera that have been found in North America (BEN # 198), a few notes about the different genera (BEN # 199) and literature references (BEN # 200).
Readers are asked to accept the comments presented here as *brief notes* offered in the hope that they will be of some help in understanding the taxonomic changes that have occurred in the tribe. It is not a careful review article. I shall be preparing a review of the evolution and taxonomic treatment of the tribe this summer for presentation at the International Monocot Symposium in Sydney, Australia, this fall, but not until after summer school is over. The comments presented are my own, but I have benefited from discussions with many other individuals over the years and considered several alternative points of view.
The Hordeae is very poorly suited to the straight jacket required by the rules of nomenclature and cladistic methodology for the majority of its species are alloploids that combine, not always in the same manner, the morphological characteristics of their progenitors. The morphologically circumscribed genera recognized by Bentham (1882), Hackel (1887), and adopted by Hitchcock (1935, 1951), and hence used in all but the most recent North American floras were undoubtedly easier to recognize than the genera recognized in the Manual. There is also ample evidence that they were artificial and, hence, had no predictive value.
The generic treatment in the Manual reflects the cytological findings of many individuals, but it is also supported, by and large, by the molecular data that are being obtained and by traditional morphological characters, albeit not the same characters as were used by Bentham, Hackel, and Hitchcock. Current disagreements are essentially over to what extent a genus should be morphologically consistent and to what extent must be morphologically distinct. Accepting wider generic limits would make writing a generic key easier, but would place together entities that the data suggest represent different lineages. "Lineages" in the context of polyploid taxa may seem strange, but all I mean is that members of the same polyploid genus have similar ancestors. This is not the equivalent of saying that genomic constitution should determine generic limits. Nevertheless, so far as I am aware, the genomic data are more highly correlated with the morphological, distributional, and molecular data available for the tribe than any other single character.
The key is based on morphological characters. Some of the larger genera contain morphologically distinct subgroups. These often come out in different portions of the key. Some taxonomists, e.g., Clayton and Renvoize (1986) and Baden et al. (1997) treat such entities as genera.
One other comment: Dr. J.R. Reveal has found a publication of a tribal name based on Hordeum that antedates the first use of a name based on Triticum. I have, therefore, with some muttering, reverted to Hordeae for the tribe that is now known to many as Triticeae.
Tribal description: Plants annual or perennial, cespitose or rhizomatous. Culms usually erect, not branched above the base. Ligules membranous; auricles often present. Inflorescence usually a single, terminal, bilateral spike or spicate raceme, often paniculate in Leymus condensatus; disarticulation beneath the spike, in the rachis, or beneath the florets, sometimes also beneath the glumes. Spikelets with 1 to several bisexual florets, sterile or staminate florets (if present) distal or solitary. Glumes subulate to lanceolate, awned or unawned, membranous to coriaceous, absent or almost absent in some species; lemmas lanceolate, 5(7)-veined, unawned or terminally awned; lodicules 2-3 mm, hyaline, usually ciliate; anthers 3, yellow; ovary apex distinctly pubescent. Caryopses longitudinally sulcate. x = 7.
I have just received a CD, Plant Family Album, vol. 1 The Rosidae. It is SUPERB! It contains illustrated descriptions of plant families in the Rosidae. The illustrations are a combination of photographs (mostly) and colored drawings, of excellent quality, and fully labelled. Words in each family are linked to a box that provides a quick definition and offers the opportunity to go to the illustrated glossary or back to the page one was reading in the first place. The design of the pages is both attractive and functional. The glossary is detailed and superbly illustrated, as is every part of the CD that I have looked at.
Another great feature is the quiz section. This offers a choice between family recognition, multiple choice, and matching - but they are much better quiz questions than those words suggest. Matching requires dragging several different labels to the right portion of the illustration. There were 7 labels on one of the pages that I looked at, eight on the other. One multiple choice question that I looked at had a picture and three sets of words - in other words, three questions. Another had six families and six pictures of ovary cross-sections to be matched up. Clear cross-sections.
I am about to ask each the main library, the Natural Resources library, and the biology department to order copies. I had several future biology teachers with me as I took a look at it and all agree that they want the high schools that employ them to have it. And the herbarium assistant has been fascinated with it for the last half hour. Buy this CD. It is excellent.
One can, of course, always come up with suggestions for improvement. The one feature that I would like is the ability to specify which families are to be included in the review quizzes. But this is minor. Drs. Waterway and Rimmer are to be congratulated on producing a superb CD for learning about families in the Rosidae.
Cost is $US 49.95 + applicable taxes, plus $6.00 shipping and handling. E-mail is WATERWAY@AGRADM.LAN.MCGILL.CA or write to Dr. Marcia J. Waterway, Plant Science Department, Macdonald Campus, McGill University, 21,111 Lakeshore Road, Ste-Anne de Bellevue, Quebec, CANADA H9X 3V9