Class Monocotyledonae
ACORUS/ACORACEAE 1077 CLASS MONOCOTYLEDONAE Plants usually herbaceous—in other words, lacking regular secondary thickening (except Palmaceae, 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 por- tion 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, Smilacaceae, Marantaceae, and some Orchidaceae); perianth with dissimilar inner and outer whorls (petals and sepals), or all parts about alike (tepals), the parianth 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 in 2,652 genera arranged in 84 families (Mabberley 1997); 25 of these families occur in nc TX. The monocots appear to be a well-supported monophyletic group derived from within the monosulcate Magnoliidae group of dicots (Chase et al. 1993; Duvall et al. 1993; Qiu et al. 1993). From the cla- distic standpoint, the dicots are therefore paraphyletic and thus inappropriate for formal recog- nition (see explantion and Fig. 41 in Apendix 6). Within the monocots, Acorus appears to be the sister group to all other monocots, with the Alismataceae (and Potamogeton) being the next most basal group (Duvall et al.
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