BEN # 197

Adolf Ceska aceska at VICTORIA.TC.CA
Sat Jul 11 03:42:54 EST 1998


                                                   
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 at 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 at 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 at 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 at 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 at victoria.tc.ca
BEN is archived at   http://www.ou.edu/cas/botany-micro/ben/
________________________________________________________________




More information about the Plantbio mailing list