Mitrastemonaceae Mak.

Genera Included: Monogeneric - Mitrastema. Parasitic on Fagaceae (Castanopsis, Lithocarpus, Quercus, Trigonobalanus) in both Old and New World. The two species are widely disjunct: M. yamamotoi (Japan, Malaysia, New Guinea) and M. matudae (Central America). The following description borrows heavily from the recent monograph by Meijer and Veldkamp (1993).

Habit: Achlorophyllous, holoparasitic herbs.

Parasitism: root endoparasites, often producing witches' brooms. Parasites may form a fairy ring around the host.

Roots: the filamentous endophyte exists inside the host root tissues, eventually anastomosing to form a network which completely surrounds the root in the phloem just outside the cambial layer. These cortical strands run longitudinally with the host root whereas the sinkers run radially into the xylem.

Stem: Absent

Leaves: "Sessile, scale-like, decussate or rarely whorled in 3-7 (-24) pairs, becoming larger upward, cream-coloured or milky yellowish-white at early flowering stage" (Meijer and Veldkamp1993).

Inflorescence: Pedicel erect, terete or quadrangular, 4-12 cm long by 0.6-1.5 cm wide. Flowers occur singly at apex of pedicel. Inflorescence breaks through the host bark leaving at its base a persistent, corky, lenticellate cupular structure, mainly composed of host tissue.

Plant Sex: Bisexual, protandrous, actinomorphic.

Flowers:
Calyx: Perianth much reduced, collars-shaped, usually irregularly crenately lobed in M. yamamotoi, 4-lobed in M. matudae.
Nectary: produced from the flowers but apparently accumulates in the scale leaves (Beehler 1994).
Androecium: stamens connate into a tube (androphore) crowned by a fertile zone of pollen-bearing cavities (locules). The connate staminal tube that is open at the top by a small hole, circuscissally splits as it is pushed up by the growing gynoecium. Apical portion (connective) sterile, below this a series of vertical rings of ca. 10 anthers each. Anthers minute, each with extrorse longitudinal slits (pores?).
Pollen: dicolpate.
Gynoecium: Ovary is superior (hypogynous), ellipsoid, 1-locular, apex half conical with a narrow groove below the style. Style 1, slightly constricted, stigma thick, conical, sub-bilobed. Placentation deeply parietal with 8-15 (-20) unequal placental lobes filling the locule.
Ovule: small (190 X 120 um), numerous, anatropous, unitegmic (but with 2 layers), tenuinucellar.

Pollination: by flies, bees, wasps, fireflies, butterflies and birds. For the latter, Beehler (1994, Biotropica 26:459) describes how canopy-dwelling honeyeaters aggressively defend their nectar source in Papua New Guinea.

Fruit: A slightly woody berry-like capsule, dehiscing along a horizontal slit along the groove between the style and ovary.

Seed: Sticky, seed coat hard (from inner integument), yellow to dark brown, reticulate when dry (collapsed cell walls); funiculus short.

Embryology:

Embryo sac is of the Polygonum type (Cocucci 1983)
Embryo: minute, undifferentiated, 4-celled (only!)
Endosperm development is ab initio cellular. Mature endosperm (10-15 cells) a sweet, oily, jelly-like pulp surrounding the embryo.

Chromosomes: X=20 for both species.

Link to Family Description of in Delta