LILIACEAE (Lily Family)
Plants perennial herbs with rhizomes, corms, or bulbs. Leaves alternate or all basal
or nearly so, less commonly whorled, the leaf blades flat, folded
longitudinally, or less commonly tubular, the bases often forming sheaths. Main
veins parallel, the secondary veins sometimes prominent and forming a network.
Inflorescences racemes, spikes, umbels, panicles, or 1-flowered, the flowers
often subtended by bracts. Flowers usually perfect, less commonly some of the
flowers functionally unisexual or the plants dioecious, radially symmetric or
less commonly somewhat bilaterally symmetric, with 3 sepals and 3 petals, these
similar or dissimilar, free or less commonly fused basally or into a tube, the
sepals usually colored. Stamens 6 or rarely 3. Ovary 1 per flower or sometimes
deeply 3-lobed and appearing as 3 separate carpels, superior or inferior, with
3 locules. Styles 1 or 3 per flower, if 1 then entire or 3-lobed. Fruits
capsules or berries, with few to many seeds. Two hundred eighty to 295 genera,
4,000–4,500 species, worldwide.
The Liliaceae and their relatives have received a variety of treatments in the
past, both traditionally and by modern systematists. Overall, the group is
widespread, diverse, and taxonomically complex enough that none of the
classifications proposed thus far has proven entirely satisfactory.
Traditionally, two or more families were recognized, mainly the Liliaceae and
Amaryllidaceae, which were separated either by inflorescence types (umbels vs.
other types) or by superior vs. inferior ovaries. More recently, several
researchers recognized that these classifications often split up closely
related groups, rendering them both artificial and uninformative.
Modern classifications have followed two different philosophies. The
classification followed here was advanced by Cronquist (1981, 1991) in which
most of the genera are subsumed into a huge, polymorphic Liliaceae, splitting
off a minority of smaller, specialized groups. In Missouri, these include the
Agavaceae, Dioscoreaceae, and Smilacaceae. This system has the utilitarian
advantage of circumscribing families that are easily discriminated from other
monocots, but the core family, Liliaceae, is so polymorphic as to become
difficult to circumscribe morphologically. The classification also is
relatively uninformative regarding relationships among a large number of
monocot genera, and at least the Agavaceae may still be polymorphic
phylogenetically. The logical extreme of this philosophy would be to recognize
a single, all-encompassing Liliaceae, with no segregates at all.
At the other extreme, Dahlgren and his collaborators recognized a much larger
number of families and orders (summarized and described in Dahlgren et al.,
1985). The advantage of this classification is that most of the family units
recognized circumscribe monophyletic (natural) groups of genera. However, in
practice it seems almost impossible to construct a key to distinguish among
these families unambiguously without resorting to couplets that actually
separate individual genera. This is because the characters used by Dahlgren et al.
(1985) to delineate families are primarily cytological, phytochemical, and
anatomical, rather than morphological.
Thus, for strictly practical reasons, the present treatment accepts the
Liliaceae in the broad sense of Cronquist (1982, 1991), with only the
Agavaceae, Dioscoreaceae, and Smilacaceae treated separately. However, for
those readers who are curious about how the 30 native and introduced genera of
these families found in Missouri were classified by Dahlgren et al. (1985), the
following list indicates their placement into 14 families:
Allium, Dichelostemma, Nothoscordum
Hymenocallis, Leucojum, Narcissus
Convallaria, Maianthemum, Polygonatum
Camassia, Muscari, Ornithogalum, Scilla
Erythronium, Lilium, Medeola
Amianthium, Melanthium, Stenanthium, Veratrum, Zigadenus
The following key to genera will work only for the Missouri representatives of
the included genera and is based primarily upon flower structures. Readers should
note that several additional genera of Liliaceae, such as Tulipa L.
(tulip), Hosta Tratt. (hosta), and Hyacinthus L.(hyacinth), are
commonly cultivated as ornamentals in the state. These persist at old homesites
but have not been reported as naturalized to date and are not treated here.