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:

Agavaceae Manfreda, Yucca

Alliaceae Allium, Dichelostemma, Nothoscordum

Amaryllidaceae Hymenocallis, Leucojum, Narcissus

Asparagaceae Asparagus

Convallariaceae Convallaria, Maianthemum, Polygonatum

Dioscoreaceae Dioscorea

Hemerocallidaceae Hemerocallis

Hyacinthaceae Camassia, Muscari, Ornithogalum, Scilla

Hypoxidaceae Hypoxis

Liliaceae Erythronium, Lilium, Medeola

Melanthiaceae Amianthium, Melanthium, Stenanthium, Veratrum, Zigadenus

Smilacaceae Smilax

Trilliaceae Trillium

Uvulariaceae Uvularia

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.