3/2; Perennial Many Spiral Southern Africa) Sphaerocyperus (1/1) Perennial One Distichous Volkiella (1/1) Annual One Distichous Genus (total/ Dispersal Nutlet Photosynthetic studied species) unit orientation type Alinula (4/2) Nutlet Dorsiventral
The genus Hymenasplenium is defined by the unusual dorsiventral
vascular system in long creeping rhizomes, swollen petiole bases and a chromosome number of x=39, 38, which differ from the radially symmetrical steles, non swollen petiole bases and chromosome number of x=36 typical of Asplenium (Murakami and Moran, 1993).
The dorsiventral microsporophylls bore two sporangia on the lower surface and were arranged in a close spiral on the axis of a strobilus, sterile scales being absent.
The fertile portion of the dwarf shoot had thus become basal, and the entire seed-scale complex had developed dorsiventral symmetry.
The evolution of the vascular system in ferns with special reference to dorsiventral
The uniaxial, dorsiventral
, strap-shaped gametophyte of the terrestrial Huperzia species lacks a ring meristem.
Mesophyll: 0, dorsiventral
or isolateral; 1, inverted dorsiventral
The microsporangia are dorsiventral
, but occasionally radial symmetry is displayed, at least near the strobilus apex, a condition also observed in the Cephalotaxaceae (Wilde, 1975).
The two series of apical segments are strongly correlated with the dorsiventral
symmetry of the shoot system.