From the early nineteenth century many of the species in this group of plants were put into a very broadly defined family, Liliaceae sensu lato or s.l.

In some groups (such as the genus Trillium in the Liliaceae), the tepals have become clearly differentiated so that the flower has three coloured petals and three smaller green sepals.

The morphological concept of petaloid monocots has been equated with "animal-attracting" (that is, for pollination) as opposed to wind-pollinating plants (such as grasses) that have evolved very different floral structures.

For example, the six tepals of cannas are small and hidden under expanded and brightly coloured stamens or staminodes which resemble petals and may be mistaken for them.

Various successive taxonomies of the monocots also emphasized the grouping of species with petaloid (undifferentiated) perianths, such as Bentham and Hooker's Coronarieæ and Hutchinson's Corolliferae ("Corolla bearing") (1936).

[17] When classification systems were based on morphological characters alone, lilioid species which clearly departed from the "lily" pattern were easily placed into separate families.

[18][17][a] The development of DNA sequencing[19] and the use of genetic data in determining relationships between species of monocots[20][21] confirmed what many taxonomists had long suspected: Liliaceae s.l.

For instance, Dahlgren had based monophyly on a single synapomorphy, that of a petaloid perianth,[24] yet in discussing his Lilliflorae admitted it was undoubtedly paraphyletic.

[b] Dahlgren treated the monocots as split between ten superorders and placed five orders (Dioscoreales, Asparagales, Liliales, Melanthiales, Burmanniales and Orchidales) in his Liliiflorae.

[26] In the 1995 study by Chase et al. referred to above, which was the largest yet to use purely molecular data, the results demonstrated paraphyly of the lilioids.

They named these alismatids, aroids, stemonoids and dioscoreoids, in addition to Acorus, and a core group of Asparagales, Liliales and commelinoids.

The Asparagales formed two major groupings, which they labelled "higher" and "lower asparagoids", and included both the Iridaceae and Orchidaceae from Dahlgren's Liliales.

[27] These findings, presented at the first Monocot Conference in 1993,[28] with the addition of several studies that had become available in the interim, formed the basis of the 1998 consensus Angiosperm Phylogeny Group (APG) ordinal scheme.

The last four were however grouped together in the resulting cladogram and most closely represent the concept of lilioids, although this left some unplaced monocot families, including Corsiaceae and Petrosaviaceae.

[31] The Monocot Conference devoted an entire section to Systematics of the Lilioids[32] and included an update of their previous research by Chase and colleagues.

[33] On this occasion the latter felt that there was now enough data to put forward a definitive classification, defining the Lilioids as comprising the four orders placed in Lilianae by Kubitzki.

[35] The second version of the APG coincided with the third Monocot Conference (2003),[36] the findings from which, using additional molecular markers, helped to resolve some of the remaining questions regarding relationships within this assemblage.

[37][38] Petrosaviaceae was shown to be included in what Chase refers to as "liliids" and placed in order Petrosaviales, while Dioscoreales and Pandanales were demonstrated to be sister clades.

[45] The cladogram shown below displays the orders of Lilianae sensu Chase & Reveal (monocots) based on molecular phylogenetic evidence.

[47] Numbers indicate crown group (most recent common ancestor of the sampled species of the clade of interest) divergence times in mya (million years ago).

Petrosaviales are a very small order (1 family, 2 genera, about 5 species) of rare leafless achlorophyllous, mycoheterotrophic plants found in dark montane rainforests in Japan, China, Southeast Asia and Borneo.

They are characterized by having bracteate racemes, pedicellate flowers, six persistent tepals, septal nectaries, three almost distinct carpels, simultaneous microsporogenesis, monosulcate pollen, and follicular fruit.

The tuberous roots form a staple food in tropical areas and have been a source of extraction of steroids for oral contraceptives.

[51] Liliales are a large size order (10 families, 67 genera, about 1,500 species) distributed worldwide, particularly in subtropical and temperate regions in the Northern Hemisphere.

[52] Asparagales are a large very diverse order (14 families, 1,122 genera, about 36,000 species), including many geophytes, ornamental flowers, vegetables, and spices.