[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
BEN # 197
BBBBB EEEEEE NN N ISSN 1188-603X
BB B EE NNN N
BBBBB EEEEE NN N N BOTANICAL
BB B EE NN NN ELECTRONIC
BBBBB EEEEEE NN N NEWS
No. 197 July 11, 1998
aceska@victoria.tc.ca Victoria, B.C.
-----------------------------------------------------------
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
-----------------------------------------------------------
GRASSES OF THE TRIBE HORDEAE IN NORTH AMERICA: 1. INTRODUCTION
From: Mary Barkworth <stipoid@cc.usu.edu>
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 intro-
duction (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 Sym-
posium 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 re-
quired 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 recog-
nize 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 lon-
gitudinally sulcate. x = 7.
NEW CD: PLANT FAMILY ALBUM, VOLUME 1 - ROSIDAE
From: Mary Barkworth <stipoid@cc.usu.edu>
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 combina-
tion 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 oppor-
tunity 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 improve-
ment. 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 congratu-
lated 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
----------------------------------------------------------------
Submissions, subscriptions, etc.: aceska@victoria.tc.ca
BEN is archived at http://www.ou.edu/cas/botany-micro/ben/
________________________________________________________________