keys to the vascular plants of east texas - Botanical Research ...

CLASS MONOCOTYLEDONAE
MONOCOTYLEDONAE 405
Plants usually herbaceous—in other words, lacking regular secondary thickening (though
stems wood-like in Palmae, Smilacaceae, most Agavaceae, and a few Poaceae); seedlings usually
with 1 seed leaf or cotyledon; stems or branches elongating by apical growth and also by
growth of basal portion of internodes; leaves when present alternate, whorled, basal, or rarely
opposite, elongating by basal growth (readily seen on spring-flowering bulbs whose leaf-tips
have been frozen back); leaf blades usually with parallel or concentrically curved veins, these
unbranched or with inconspicuous, short, transverse connectives (leaves net-veined or with
prominent midrib and spreading side-veins parallel with each other in Alismataceae, Araceae,
Cannaceae, Marantaceae, some Orchidaceae, and Smilacaceae); perianth with dissimilar inner
and outer whorls (petals and sepals) or all parts � alike (tepals); perianth parts separate or
united, commonly in 3s, less often in 2s, rarely in 5s, or perianth of scales or bristles, or entirely
absent.
AWorldwide, the Monocotyledonae is a group composed of ca. 55,800 species (ca. 22% of the
flowering plants) in 2,652 genera arranged in 84 families (Mabberley 1997); 46 of these families
occur in East TX. The monocots appear to be a well-supported monophyletic group (e.g., Chase
et al. 1993; Duvall et al. 1993b; Qiu et al. 1993, 1999; Soltis et al. 1997, 1999, 2000; Savolainen et al.
2000) derived from non-eudicots (the non-eudicots, including the monocots and many
Magnoliidae, have pollen grains with a single aperture, while the eudicots have pollen grains
with three apertures). More specifically, recent analyses indicate that the monocots are part of a
“eumagnoliid” clade containing a number of Magnoliidae orders (Winterales, Piperales, Laurales,
Magnoliales, and Chloranthales) (Chase et al. 2000; Soltis et al. 2000) including plants often referred
to as woody magnoliids (e.g, Magnoliaceae) and paleoherbs (e.g, Aristolochiaceae). From
the cladistic standpoint, since monocots are derived from within the dicots, the dicots are paraphyletic
and thus inappropriate for formal recognition (see explantion and Fig. 174 in Appendix 3
and also Appendices 5 and 6). Within the monocots, Acorus appears to be the sister group to all
other monocots, with the Alismatales (including Araceae and Hydrocharitaceae) being the
next most basal group (Duvall et al. 1993b; Chase et al. 2000; Fuse & Tamura 2000; Soltis et al.
2000; Duvall 2001). However, numerous unresolved questions still exist, as emphasized by differences
in the system of Reveal and Pires (2002) (e.g., recognition of Arales as a lineage separate
from Alismatales, which are possibly paraphyletic). Recent advances in the understanding
of monocot phylogeny (e.g., Dahlgren et al. 1985; Goldblatt 1995; Chase et al. 2000; Soltis et al.
2000) have resulted in considerable rearrangement of the monocots at the family and order levels.
One of the most striking examples is that the Liliaceae in the traditional broad sense is now
known to be a group of superficially similar species in four different orders: Liliales,
Asparagales, Alismatales (Tofieldiaceae), and Dioscoreales (Nartheciaceae) (Chase et al. 2000).
As such, this polyphyletic assembladge must be split into a number of smaller, taxonomically
defensible families (see further discussion under Liliaceae and in Appendix 6). This said, there
is currently no concensus on the exact number of families that should be recognized in the
Liliaceae (broad sense) or in the monocots as a whole, with differences due to both taxonomic
philosophy (e.g., the allowability of paraphyletic families) and lack of conclusive data. The
name “monocotyledon” is derived from the presence of a single cotyledon (= seed leaf), in contrast
to the two seed leaves found in the dicotyledons.
REFERENCES: Cronquist 1981, 1988, 1993; Dahlgren et al. 1985; Conran 1989; Thorne 1992a, 1992b;
Chase et al. 1993; Clark et al. 1993; Duvall et al. 1993b; Qiu et al. 1993, 1999; Reveal 1993a, 1993b;
Bharathan & Zimmer 1995; Chase et al. 1995a, 1995b, 2000; Goldblatt 1995; Herendeen & Crane
1995; Les & Haynes 1995; Les & Schneider 1995; Rudall & Cutler 1995; Rudall et al. 1995, 1997;
Stevenson & Loconte 1995; Soltis et al. 1997, 2000; Takhtajan 1997; Angiosperm Phylogeny
Group 1998; Kubitzki et al. 1998; Bremer 2000; Duvall 2000; Fuse & Tamura 2000; Savolainen et