notes Habit of a single leafy shoot of Maianthemum dilatatum. Thanks to Doreen Smith for pointing out this plant to me in the field. Note that this is not necessarily an entire plant...Maianthemum species are rhizomatous, so a single plant can have several separate above ground stems (called shoots or ramets) emanating from its underground rhizome. A typical plant of Maianthemum dilatatum will have a number of single-leaved shoots as well as flowering shoots with 2-3 leaves and a terminal inflorescence.
This particular flowering shoot is somewhat remarkable in having 4 leaves (I think...it's a bit hard to tell whether the lowest leaf is actually part of the main shoot here...or perhaps the initial leaf of another shoot coming up next to it). The species descriptions in both the Jepson eFlora and the FNA state 'leaves 2-3'...but the much more detailed description in LaFrankie's 1986 paper ''Morphology and taxonomy of the New World species of Maianthemum (Liliaceae)'' indicates there can sometimes be 4 'foliage' leaves on the fertile stems (as opposed to the single leaves of non-flowering stems growing off the plant's rhizome...or the tiny, scale-like underground leaves on the rhizome itself).
An interesting aspect of M. dilatatum is that its flower are dimerous...meaning there are two whorls of 2 tepals, two whorls of 2 stamens, and 2 carpels. (This structure is also referred to less technically as 4-merous in reference to the 4 tepals and 4 stamens.) M dilatatum and its two very closely related congeners, the eastern North American M. canadense and east Asian M. bifolium are the only dimerous members of the genus Maianthemum, the other 27 or more species worldwide are trimerous (6 tepals, 6 stamens, 3 carpels). The trimerous species were formerly placed in the genus Smilacina.
The vast majority of monocots have flower parts in whorls of 3. I wonder if there are any 4-merous taxa other than the three Maianthemum species within Liliaceae (sensu lato)? I researched a bit, but wasn't able to find the answer to that question. [Note: In recent years the formerly large, and paraphyletic Liliaceae ''sensu lato'' has been split by different taxonomic camps into various schemes of orders and families. Maianthemum was recently moved from Liliaceae into the smaller family Ruscaceae in the Jepson treatment. In the APG III system, Maianthemum is placed in the subfamily Nolinoideae of family Asparagaceae and order Asparagales...i.e. it's not even in the order Liliales! Flowers are typically trimerous in Liliaceae sensu lato.]
