thyrse = a type of inflorescence. But it is not clear what Masters might have referred to.
WCM Protologue Reference:
(Mast.) Pillans, Ann. Bolus Herb. 3: 146 (1922)
Vegetative parts: plants clumped, 1–1.5 m tall, basal diameter 1–3 m, crown diameter 1–3 m, with rhizomes. Rhizome spreading, unbranched or sparsely branched, culms evenly spaced, 3.5–5 mm in diam., culms 10–30 mm apart. Fertile culms unbranched, round (not compressed), solid or with a small central cavity, smooth or finely rugulose, green or olivaceous, 1–1.5 m tall, diameter at base 3–5 mm, diameter at apex 2–3.5 mm. Clusters of sterile branches at the nodes of the fertile branches absent. Sheaths more than 1 per culm, dropping off, with an abscission line present, loosely convoluted, 30–75 mm long, margins entire, reddish to dark brown with slightly uneven colouring, upper 1/3 in colour and texture similar to the lower 2/3, apical margins coriaceous, like the rest of the body or narrowly membranous, hyaline shoulders absent, apex, excluding the membranous lobes, acute or obtuse. Sheath-mucro absent or penicellate, straight and erect, 0.1–0.3 mm long, some sheaths have a very narrow membranous margin,mostly they are entirely cartilaginous. Males: male inflorescence with 50–100 spikelets or 101–500 spikelets, paniculate, 80–200 mm long, 10–20 mm wide. Male inflorescence spathes caducous, taller than spikelets, cartilaginous, spathes are of the same colour throughout. Male spathellae inconspicuous or absent or conspicuous (only those spathellae subtending several brances of spikelets are quite conspicuous), 6–10 mm long. Male flowers in spikelets. Male spikelets erect on stiff pedicels or sessile, undifferentiated, apex undifferentiated, 3–4.5 mm, 2.5–3.5 mm, with 2–8 flowers, pedicels shorter than the spikelets, terete or angular. Male bracts shorter than flowers, 0.5–1.3 mm long, ovate or orbicular, rounded, cartilaginous, bract upper margin like body of bract, bract awn minute or absent, sturdy and rounded, usually there are two subtending the flower, indicating the presence of sterile bracts. Male flower 2–3 mm long. Male tepals sepals and petals the same rigidity, cartilaginous, oblong, inner tepals longer than outer tepals. Male outer lateral tepals keeled or winged, glabrous. Anthers 1.2–1.6 mm long, included in the flowers. Females: female inflorescence interrupted or linear, 100–250 mm long, 10–15 mm wide, with 6–10 spikelets or 11–20 spikelets. Female spathes longer than the spikelets, obscuring spikelet, persistent, cartilaginous. Female spathellae inconspicuous or absent or conspicuous (only spathellae subtending several branches of spikelets/flowers are conspicuous), 6–10 mm long. Female spikelet pedicel sparsely branching, undifferentiated, apex undifferentiated, 3–5 mm long, with 1–3 flowers, with 0 sterile bracts. Female bracts shorter than flowers, erect, 0.5–1 mm long, ovate, rounded or obtuse or acute, cartilaginous, apical margin like rest of bract, same as body of bract, awn minute or absent. Female flower 3–4 mm long, without a fleshy pedicel, six tepals. Female tepals cartilaginous, glabrous and smooth, at least as tall as nut, wrapped around it and obscuring the surface, midrib raised, margins entire, apices rounded or obtuse or acute, inner and outer whorls the same length. Female outer lateral tepals conduplicate, hidden by bracts, or bracts are shorter than flowers, 1.7–2 mm long. Female odd outer tepal oblong, 1.7–2 mm long. Female inner tepals oblong or ovate, 2–3 mm long. Staminodes present. Styles feathery, 3. Style bases free. Ovary with 1 locule, indehiscent. Fruit: indehiscent fruits with a softer ovary wall. Perianth presence on fruits persistent, papery to leathery, not winged. Nut apex smooth, without a distinct cap, wall smooth, (1.92–)2.54(–3.2) mm long, (1.2–)1.4(–1.68) mm diam., shape in side view elliptical or ovate, shape in top view elliptical in cross section, brown or black, mode of seed release for nutted plants unknown. Elaiosome absent.