Merostachys

HABIT Perennial. Rhizomes absent (2), or short (45); pachymorph (45/45). Culms erect (26/36), or arching (3/36), or leaning (3/36), or scandent (5/36); 150–986.3–3000 cm long; woody; without nodal roots (1/1). Culm-internodes terete. Culm-nodes flush with internodes (1/10), or swollen (9/10); without obvious supra-nodal ridge (2/5), or with distinct supra-nodal ridge (3/5). Lateral branches dendroid. Branch complement three (1/46), or several (3/46), or many (43/46); flabellate; with subequal branches (6/6); thinner than stem (22/22). Culm-sheaths tardily deciduous (1/28), or deciduous but leaving a persistent girdle (2/28), or deciduous (25/28); without auricles (1/4), or auriculate (3/4). Culm-sheath blade linear (4/22), or lanceolate (18/22); constricted at base (1/1). Leaf-sheath auricles absent (43), or erect (3), or falcate (1). Ligule an eciliate membrane (3), or a ciliolate membrane (43), or absent (1). Leaf-blade base with a brief petiole-like connection to sheath. Leaf-blades linear (3), or lanceolate (38), or elliptic (1), or oblong (16), or ovate (11). Leaf-blade midrib indistinct (2/2). Leaf-blade venation without cross veins (41), or with obscure cross veins (1), or with distinct cross veins (5).

INFLORESCENCE Inflorescence composed of racemes (41/41); exserted (35/41), or embraced at base by subtending leaf (7/41). Peduncle cylindrical at apex (1/1), or tipped by a glumaceous appendage (1/1).

Racemes single (41/41); unilateral (41/41); bearing 1–19–40 fertile spikelets on each. Rhachis angular (15/15); terminating in a spikelet (1/41), or sterile spikelet (40/41). Spikelet packing broadside to rhachis (41/41); crowded (3/41), or contiguous (34/41), or lax (3/41), or distant (1/41); 2 -rowed (7/7).

Spikelets appressed (1/30), or spreading (3/30), or pectinate (25/30), or deflexed (2/30); solitary (36/39), or in pairs (4/39), or in threes (1/39). Fertile spikelets sessile (14/41), or pedicelled (27/41); 1 in the cluster (1/2), or 2 in the cluster (2/2), or 3 in the cluster (1/2); the upper smaller (1/1). Pedicels free (26/27), or fused to each other (1/27); oblong (9/9).

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets (9/10), or 2 basal sterile florets (1/10); 1 fertile florets (37/41), or 2 fertile florets (6/41), or 3–4 fertile florets (1/41), or 5 fertile florets (2/41), or 6–10 fertile florets (1/41); with a barren rhachilla extension (20/41), or with diminished florets at the apex (23/41). Spikelets lanceolate (13/41), or elliptic (24/41), or oblong (2/41), or ovate (2/41), or cuneate (1/41); laterally compressed (41/41); 4–13.95–55 mm long; breaking up at maturity (41/41); disarticulating below each fertile floret (41/41). Rhachilla internodes brief up to lowest fertile floret (39/41), or elongated below proximal fertile floret (2/41); definite (8/8); glabrous (7/8), or pubescent (1/8). Floret callus pubescent (1/1).

GLUMES Glumes one the lower absent or obscure (9/41), or two (33/41); persistent (41/41); shorter than spikelet (36/41), or reaching apex of florets (4/41), or exceeding apex of florets (1/41). Lower glume linear (3/33), or lanceolate (15/33), or elliptic (3/33), or ovate (13/33); clasping (1/1); 0.25–0.3883–0.5 length of upper glume; membranous (10/28), or chartaceous (18/28); without keels (10/23), or 1-keeled (13/23); 0 -veined (1/27), or 1 -veined (23/27), or 3 -veined (1/27), or 5 -veined (1/27), or 9–11 -veined (1/27). Lower glume lateral veins absent (23/33), or distinct (9/33), or prominent (1/33). Lower glume surface without pits (33/33); glabrous (18/33), or puberulous (11/33), or pubescent (4/33). Lower glume apex acute (13/30), or acuminate (14/30), or attenuate (2/30), or setaceously attenuate (2/30); muticous (30/33), or mucronate (2/33), or awned (1/33). Upper glume lanceolate (12/41), or elliptic (6/41), or oblong (1/41), or ovate (21/41), or orbicular (1/41); 0.01–0.6656–1 length of adjacent fertile lemma; membranous (14/41), or chartaceous (27/41); without keels (4/9), or 1-keeled (5/9); 0–9–17 -veined. Upper glume primary vein eciliate (39/40), or pubescent (1/40). Upper glume lateral veins without ribs (37/38), or ribbed (1/38); transversely connected at apex (3/6), or with cross-veins (3/6). Upper glume surface smooth (34/41), or asperulous (4/41), or scabrous (3/41); glabrous (27/41), or puberulous (9/41), or pubescent (4/41), or hispid (1/41). Upper glume apex obtuse (1/39), or acute (19/39), or acuminate (15/39), or attenuate (2/39), or setaceously attenuate (1/39), or caudate (1/39); muticous (28/41), or mucronate (5/41), or awned (8/41); 1 -awned (8/8).

FLORETS Basal sterile florets barren (10/10); without significant palea (10/10). Lemma of lower sterile floret elliptic (3/10), or oblong (1/10), or ovate (7/10); 0.5–0.75–1 length of fertile lemma; chartaceous (4/4); 5 -veined (1/5), or 7 -veined (3/5), or 15–17 -veined (1/5); without grooves (8/10), or sulcate (2/10); obtuse (2/9), or acute (5/9), or acuminate (2/9); muticous (7/10), or mucronate (3/10). Fertile lemma linear (1/41), or lanceolate (13/41), or elliptic (3/41), or oblong (5/41), or ovate (23/41); chartaceous (33/41), or cartilaginous (2/41), or coriaceous (6/41); without keel (39/41), or keeled (2/41); wingless (41/41); 5–14–23 -veined. Lemma lateral veins obscure (1/2), or distinct (1/2), or prominent (1/2). Lemma surface smooth (35/41), or granulose (1/41), or scaberulous (5/41); unwrinkled (41/41); without grooves (41/41); glabrous (14/41), or puberulous (14/41), or pubescent (13/41), or pilose (1/41). Lemma margins eciliate (28/41), or ciliolate (3/41), or ciliate (8/41), or pubescent (1/41), or woolly (1/41). Lemma apex acute (28/33), or acuminate (5/33); muticous (36/41), or mucronate (4/41), or awned (1/41); 1 -awned (1/1). Palea 1–1.004–1.1 length of lemma; membranous (12/41), or chartaceous (25/41), or cartilaginous (2/41), or coriaceous (2/41); 2 -veined (3/18), or 6–7 -veined (1/18), or 8 -veined (3/18), or 9 -veined (1/18), or 10 -veined (4/18), or 11 -veined (3/18), or 12 -veined (7/18), or 13–14 -veined (2/18). Palea keels separated (14/41), or approximate (1/41), or contiguous above a sulcus (26/41); smooth (38/41), or scaberulous (2/41), or scabrous (1/41); eciliate (27/41), or ciliolate (12/41), or ciliate (1/41), or woolly (1/41). Palea surface glabrous (34/41), or puberulous (4/41), or pilose (2/41), or woolly (1/41). Palea apex muticous (40/41), or with excurrent keel veins (1/41). Apical sterile florets resembling fertile though underdeveloped (1/23), or distinct from fertile (22/23); 1 in number (21/21); rudimentary (19/21), or linear (2/21).

FLOWER Lodicules 3 (40/40); membranous (1/1); glabrous (32/40), or ciliate (8/40). Anthers 3 (40/40). Stigmas 2 (39/40), or 3 (1/40). Ovary glabrous (1/1).

FRUIT Caryopsis with free brittle pericarp (36/36); ellipsoid (2/11), or oblong (3/11), or ovoid (6/11); smooth (2/3), or striate (1/3); apex unappendaged (1/3), or rostrate (2/3). Embryo 0.1 length of caryopsis. Hilum linear (2/2).

DISTRIBUTION South America.

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