Home Flora of Missouri
Home
Name Search
Families
Volumes
Sporobolus R. Br. Search in The Plant ListSearch in IPNISearch in Australian Plant Name IndexSearch in Index Nominum Genericorum (ING)Search in NYBG Virtual HerbariumSearch in JSTOR Plant ScienceSearch in SEINetSearch in African Plants Database at Geneva Botanical Garden Decrease font Increase font Restore font
 

Published In: Prodromus Florae Novae Hollandiae 169. 1810. (Prodr.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 8/6/2009)

 

Export To PDF Export To Word

51. Sporobolus R. Br. (dropseed)

Plants annual or perennial, sometimes with rhizomes, forming tufts or clumps. Flowering stems mostly erect or ascending (occasionally spreading in Sporobolus neglectus, S. ozarkanus, and S. vaginiflorus), glabrous or uncommonly roughened. Leaf sheaths rounded on the back or slightly angled, glabrous or variously roughened or hairy, the ligule a line or band of hairs, these often fused at the base into a minute membrane. Leaf blades flat, folded lengthwise, or with inrolled margins, glabrous or variously roughened or hairy. Inflorescences open panicles or appearing spikelike, but then at least the lowermost branches somewhat elongate and noticeable or the inflorescence linear in outline, terminal or in some species also lateral (if present, the axillary inflorescences usually all or mostly enclosed by the subtending leaf sheaths). Spikelets with 1 floret, short‑stalked, slightly to moderately flattened laterally, disarticulating above the glumes, the glumes sometimes also shed with age. Glumes slightly to strongly unequal in size, the lower glume mostly shorter than the other one and often shorter than the rest of the spikelet, the upper glume often about as long as or somewhat longer than the rest of the spikelet, 1‑nerved, keeled, glabrous or roughened along the midnerve, awnless. Lemma 1‑nerved (faintly 3‑nerved in S. ozarkanus and S. vaginiflorus), awnless, rounded on the back or keeled, the base glabrous or minutely hairy, otherwise glabrous to roughened along the midnerve or hairy with short, straight, light‑colored hairs appressed to the surface between the nerves. Palea sometimes splitting longitudinally at maturity to expose the fruit. Stamens 3. Fruits obovate to oblong or nearly circular in outline, the outer coat shed easily when moistened, sometimes turning gelatinous. One hundred to 160 species, nearly worldwide, mostly in tropical and warm‑temperate regions.

Those species of Sporobolus in which some or all of the inflorescences remain enclosed in the subtending leaf sheaths tend to reproduce cleistogamously, that is, pollen cannot be dispersed and obligately pollinates the stigmas of the same floret. The percentage of seed set in these inbred plants is usually quite high.

 

Export To PDF Export To Word Export To SDD
Switch to indented key format
1 Inflorescences relatively open panicles, narrowly elliptic to ovate or broadly triangular in outline, the branches ascending to spreading at maturity, mostly free from the subtending leaf sheaths at maturity (2)
+ Inflorescences spikelike panicles, linear to narrowly elliptic in outline, the branches appressed to the main axis or nearly so, sometimes all or mostly enclosed within the subtending leaf sheaths at maturity (5)
2 (1) Spikelets 3.2–6.0 mm long; lower glume linear to very narrowly triangular, tapered gradually to a sharp point at the tip 5 Sporobolus heterolepis
+ Spikelets 1.2–2.8 mm long; lower glume lanceolate to narrowly triangular, narrowed to a much shorter sharp point at the tip (3)
3 (2) Leaf sheaths with dense tufts of long (2–4 mm) hairs at the tips of the margins 4 Sporobolus cryptandrus
+ Leaf sheaths glabrous or occasionally with a few long hairs at the tips of the margins (4)
4 (3) Inflorescences 12–40 cm long, the lowermost branches alternate or opposite 1 Sporobolus airoides
+ Inflorescences 3–10(–15) cm long, the lowermost branches whorled 9 Sporobolus pyramidatus
5 (1) Glumes noticeably unequal in length, the lower glume 1/2–2/3 as long as the upper glume (6)
+ Glumes nearly the same length, the lower glume more than 3/4 as long as the upper glume (9)
6 (5) Spikelets 4.0–7.5 mm long (7)
+ Spikelets 1.5–2.8 mm long (8)
7 (6) Lemma and palea glabrous but usually roughened along the midnerve 3 Sporobolus compositus
+ Lemma and palea hairy (look carefully with magnification to see short, straight, light-colored hairs appressed to the surface between the nerves) 2 Sporobolus clandestinus
8 (6) Upper glume 1.5–2.2 mm long, 3/4 to about as long as the floret, lanceolate to narrowly elliptic-ovate 4 Sporobolus cryptandrus
+ Upper glume 0.8–1.3 mm long, 1/2–2/3 as long as the floret, elliptic-ovate 6 Sporobolus indicus
9 (5) Lemma and palea glabrous (10)
+ Lemma and palea hairy (look carefully with magnification to see short, straight, light-colored hairs appressed to the surface between the nerves) (11)
10 (9) Lemma 1-nerved, white or evenly tinged with purple at maturity; lowermost leaf sheaths glabrous or with a few long hairs at the tip 7 Sporobolus neglectus
+ Lemma 3-nerved, the lateral nerves sometimes faint, pale yellow and usually irregularly mottled with purple at maturity; lowermost leaf sheaths sparsely to densely pubescent with long pustular-based hairs on the margins, tip, and surface 8 Sporobolus
11 (9) Plants perennial; spikelets 4.5–7.5 mm long 2 Sporobolus clandestinus
+ Plants annual; spikelets 1.9–5.0 mm long (12)
12 (11) Glumes slightly longer than the floret; lowermost leaf sheaths hairy on the surface, noticeably inflated, appearing mostly 1.5–3.0 mm wide in profile (do not unfold) 8 Sporobolus ozarkanus
+ Glumes usually shorter than the floret; lowermost leaf sheaths often glabrous on the surface, only slightly inflated, appearing 0.8–1.7 mm wide in profile (do not unfold) 10 Sporobolus
 
 
© 2014 Missouri Botanical Garden - 4344 Shaw Boulevard - Saint Louis, Missouri 63110