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The Cycad Pages
M. calocoma
Microcycas calocoma Photo Dennis Stevenson
GENUS  Microcycas
D.W. Stevenson

Microcycas (Miq.) A. DC., Prodr. 16(2): 522-548 (1868); from the Greek micro small, and the generic name Cycas, i.e. a small Cycas. Type: Microcycas calocoma (Miq.) A. DC.
A genus of one species, M. calocoma, in the family Zamiaceae. Endemic in Cuba.
Distinguishing characters:

  • Leaves pinnate
  • Leaflets lacking a midrib
  • Leaflets articulated
  • Sporophylls in vertical rows in cones
  • Megasporophyll apices faceted or flattened, bilobed

Description:

Habit: dioecious palm-like shrubs with tall aerial, pachycaul, cylindrical stems, with many leaves. Leaf bases persistent. New leaves emerging in flushes, with distinctly apparently truncate apices. Dichotomous branching uncommon, basal offsets ("suckers") produced ocasionally.

Leaves: pinnate, spirally arranged, interspersed with cataphylls, lower leaflets not reduced to spines. Petioles lacking prickles. Longitudinal ptyxis erect, horizontal ptyxis erect. Leaflets simple, entire, with numerous bifurcating parallel veins and no distinct midrib, leaflets articulated, inserted near the edges of the rhachis towards the adaxial side, lacking a differently coloured basal gland; stomata on lower surface only or on both surfaces; epidermal cells elongated parallel to long axes of leaflets. Leaves pubescent, at least when young, with branched and simple, transparent and coloured hairs.

Microsporophylls: spirally orthostichous, aggregated into sessile male cones and each with a simple sterile apex, which is often flattened or faceted, bilobed, never produced into an upturned spine. Each microsporophyll bearing numerous microsporangia (pollen-sacs) on the abaxial surfaces. Microsporangia opening by slits. Pollen cymbiform, monosulcate.

Megasporophylls: spirally orthostichous, aggregated into sessile female cones. Sporophylls simple, appearing peltate with a simple dilated apex which is usually hexagonal, flattened or faceted, bilobed, never produced into an upturned spine. Ovules two (rarely three), sessile, orthotropous, inserted on the inner (axis-facing) surface of the thickened lamina and directed inwards ("inverted").

Seeds: subglobular to oblong or ellipsoidal, with a red, fleshy outer sarcotesta. Endosperm haploid, derived from the female gametophyte. Embryo straight; with 2 cotyledons that are usually united at the tips and a very long, spirally twisted suspensor. Seeds radiospermic; germination cryptocotular.


The Cycad Pages

© 1998-2012 Royal Botanic Gardens Sydney
Written and maintained by Ken Hill 1998-2010
Maintained by Leonie Stanberg and Dennis Stevenson 2010-2012
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