平藓科   ping xian ke

by Wu Peng-cheng

 

 

Plants small, medium-sized to rather robust, yellow to brownish green or grayish green, usually glossy, mostly complanate, in loose or compact mats. Primary stems creeping; secondary stems ascending, erect or pendulous, 1–3-pinnately branched or irregularly branched; stem in cross section rounded or oval, usually without a central strand, cortical layers composed of 3–4 layers of small, thick-walled cells and large, thin-walled inner cells. Stem and branch leaves similar or dimorphic (in the Neckeraceae, all description of stem leaves refer to secondary stem leaves), usually complanate, loosely appressed, rounded-ovate, oblong-ovate, ovate-lanceolate or lingulate, oblong-lingulate, mostly asymmetrical, plane or strongly undulate, rarely irregularly longitudinally plicate; leaf apices broadly acuminate, acute, apiculate, or rounded-obtuse to truncate; leaf bases plane, or incurved on one side or with a small lobe; margins usually serrulate to coarsely toothed above, rarely entire; costae single, slender to rather thick, sometimes double or forked, rarely absent; leaf cells mostly smooth, rarely unipapillose; upper cells usually shorter, often rounded-quadrate, rounded-polygonal, or rhombic, thick-walled; median and lower cells becoming elongate, from rhomboidal to linear, thinner-walled; basal juxtacostal cells often porose; alar cells not clearly differentiated; occasionally all cells uniform. Dioicous or autoicous. Setae very short to elongate; capsules immersed to submerged or long-exserted, subglobose, ovoid to cylindrical; opercula conic, shortly apiculate to long-rostrate; annuli not developed to well-developed; peristome double, sometimes reduced to rudimentary; exostome teeth lanceolate to linear-lanceolate, papillose or striolate at the base, rarely smooth, with low lamellae inside; endostome segments linear or linear-lanceolate, as long as the teeth or often shorter, reduced, smooth to papillose, sometimes keeled, perforate; basal membrane usually low or absent, sometimes high; cilia often absent, sometimes well-developed. Calyptrae cucullate or mitrate, smooth or somewhat hairy. Spores spherical, smooth or papillose.

1. Stems mostly tripinnately branched, dendroid, frondose, rarely unipinnately branched... 4. Homaliodendron

1. Stems often not distinctly pinnately branched, usually irregularly pinnately branched, not dendroid ............ 2

2. Secondary stems to 10 cm long; leaves mostly truncate or rounded at the apex.................... 6. Neckeropsis

2. Secondary stems usually not more than 5 cm long; leaves rounded-obtuse or obtuse at the apex............... 3

3. Leaves not strongly undulate, glossy, mostly densely appressed on stem.......................................................... 4

3. Leaves strongly undulate or not undulate, slightly glossy or not glossy, mostly loosely appressed or rarely densely appressed on stem....................................................................................................................................... 5

4. Leaves oblong-ovate or rounded-ovate, with a lobe at the distal side of base; costae absent....................... 3. Homaliadelphus

4. Leaves oblong, without a lobe at the distal side of base; costae single.......................................... 2. Homalia

5. Leaves broadly ovate or ovate-lingulate, strongly undulate or not undulate; costa mostly single, weak or indistinct, rarely bicostate; leaf cells rhomboidal to linear, thin-walled............................................. 5. Neckera

5. Leaves broadly lingulate, irregularly undulate; costae single, thick; leaf cells irregularly rhomboidal, thick-walled...................1. Himantocladium