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Pakistan | Family List | Poaceae

POACEAE Tribe ANDROPOGONEAE

Annual or perennial herbs. Leaf-blades usually flat and linear; ligule scarious or membranous, a line of hairs or absent. Inflorescence composed of fragile (very rarely tough) racemes, these sometimes in a large panicle, but usually solitary, paired or digitate, terminating the culm or axillary and numerous, in the latter case each true inflorescence subtended by a modified leaf-sheath (spatheole) and often aggregated into a leafy false panicle. Racemes bearing the spikelets in pairs (rarely singly or in threes, but usually terminating in a triad), nearly always with one sessile and the other pedicelled, these sometimes alike but usually dissimilar, the sessile being bisexual and the pedicelled male or barren (very rarely the sexes reversed), rarely the spikelets unisexual with the sexes in separate parts of the same inflorescence or in different inflorescences; occasionally with 1 or more of the lowermost pairs in a raceme (homogamous pairs) alike, infertile and persistent for some time after the other spikelets have fallen. Sessile spikelet 2-flowered, falling entire at maturity with adjacent internode and pedicel (the pedicelled spikelet usually falling separately); glumes usually as long as the spikelet and ± hardened, the lower very variable in shape and ornamentation, the upper usually boat-shaped and fitting between the internode and pedicel; lower floret male or barren, the lemma membranous or hyaline and awnless, the palea usually suppressed if floret barren; upper floret bisexual (rarely male or female), with or without a spirally twisted and geniculate awn from the membranous or hyaline lemma; palea shorter than the lemma, frequently absent; lodicules 2; stamens mostly 3; stigmas 2. Pedicelled spikelet sometimes similar to the sessile, but commonly male or barren, awnless, and smaller or even vestigial (though occasionally large and colorful); rarely the pedicel absent or fused to the internode. Grain with large embryo and punctiform hilum; starch grains simple, angular. Chromosomes small, basic number 5, 6 or 9.

Genera ± 87; throughout the tropics, extending into warm temperate regions; 36 genera and 67 species in Pakistan.

The most characteristic feature of the tribe is the occurrence of paired spikelets on fragile racemes so that the basic floral unit is a segment consisting of internode, sessile spikelet, pedicel and pedicelled spikelet. In the least modified genera the spikelets are alike, but there is a progressive loss of function in the pedicelled spikelet, coupled with a tendency for the pedicel to take part in the investment of the sessile spikelet; in extreme cases the pedicel becomes flattened and fused to the internode. Investment of the sessile spikelet is augmented in certain genera by the modification of the lowermost spikelets in the raceme to form involucral scales.

A second characteristic of the tribe is a progressive reduction in size of the inflorescence, accompanied by axillary branching and modification of the subtending leaves. Thus the large terminal panicle of the least modified genera gives way to a profusion of short racemes or raceme-pairs, each partially enclosed by an inflated bladeless sheath, and all crowded towards the top of the culm to form a complex leafy branch system which imitates a true panicle.

Zea mays Linn., Sp. Pl. 2: 971.1753 is the familiar Maize or Indian Corn (vern.: Makki) introduced to the Old World from tropical America and cultivated as a summer crop throughout Pakistan up to an altitude of about 2500 m. The male spikelets are usually collected in terminal racemes, while the solitary female in-florescence consists of numerous female spikelets seated on a spongy axis. It is discussed by Parandekar (in J. Bombay nat. Hist. Soc. 49: 473.1950), Mangelsdorf (Corn, its Origin, Evolution and Improvement, 1974) and Wilkes (The Origin of Corn: Studies of the last 100 years, 1977).

1 Spikelets all bisexual, or each bisexual spikelet paired with a male or barren one   (2)
+ Spikelets unisexual, the sexes in separate inflorescences or in different parts of the same inflorescence   (34)
       
2 (1) Pedicels and rhachis internodes slender, filiform or linear, rarely thickened upwards but then with the upper lemma awned   (3)
+ Pedicels and rhachis internodes stout, 3-angled, rounded or flattened and thickening upwards; upper lemma awnless   (28)
       
3 (2) Spikelets of each pair alike, at least one of them pedicelled   (4)
+ Spikelets of each pair different, sometimes the pedicelled much reduced or rarely suppressed but then the spikelets all alike   (11)
       
4 (3) Spikelets in ± ample panicles or compound racemes arranged along a central axis   (5)
+ Spikelets in racemes, these solitary or several, the latter digitate or subdigitate   (8)
       
5 (4) Panicle spike-like, silvery, not obviously composed of racemes   Imperata
+ Panicle open or contracted, if racemose the component racemes distinct   (6)
       
6 (5) Rhachis of racemes fragile; one spikelet of a pair sessile   Saccharum
+ Rhachis of racemes tough, not breaking up; both spikelets of a pair pedicelled   (7)
       
7 (6) Spikelets surrounded by an involucre of long golden-brown hairs arising from the callus; inflorescence composed of racemes arranged along a central axis   Miscanthus
+ Spikelets hairy but without an involucre; inflorescence an ample panicle with whorled branches   Spodiopogon
       
8 (4) Lower glume medianly grooved, glabrous   Microstegium
+ Lower glume convex or concave, often villous   (9)
       
9 (8) Raceme solitary   Pogonatherum
+ Racemes 2 or more   (10)
       
10 (9) Upper lemma minutely 2-toothed at the tip; lower glume convex on the back, not 2-keeled   Eulaliopsis
+ Upper lemma deeply bifid at the tip; lower glume flat on the back, the margins sharply inflexed-, sometimes 2-keeled at the tip   Eulalia
       
11 (3) Racemes arranged in a panicle with its common axis longer than the lowest raceme, not supported by spathes   (12)
+ Racemes solitary, paired or subdigitate, often supported by spathes   (15)
       
12 (11) Sessile spikelets dorsally compressed   (13)
+ Sessile spikelets laterally compressed or terete   (14)
       
13 (12) Pedicels and rhachis internodes with a translucent or balsamiferous median line; racemes of 1-2(-8) Sessile spikelets (if more see Bothrichloa bladhii)   Capillipedium
+ Pedicels and rhachis internodes solid   Sorghum
       
14 (12) Racemes reduced to 1 sessile and 2 pedicelled spikelets, rarely with 1 or 2 additional pairs below   Chrysopogon
+ Racemes composed of many paires of spikelets   Vetiveria
       
15 (11) Fertile lemma awned form low down on the back   Arthraxon
+ Fertile lemma awned form the tip or the sinus of the 2-toothed tip, rarely awnless   (16)
       
16 (15) Awn form the tip of the narrow fertile lemma, or if lemma awnless then racemes with an involucre composed of 2 homogamous pairs of spikelets   (17)
+ Awn from the sinus of the 2-toothed fertile lemma, or if lemma awnless then racemes reduced to 3 heteromorphous spikelets enclosed in a boat-shaped spathe   (21)
       
17 (16) Racemes composed of many pairs of spikelets   (18)
+ Racemes composed of 2 homogamous pairs of spikelets forming an involucre, and 1-4 sessile spikelets   (20)
       
18 (17) Callus pungent   Heteropogon
+ Callus obtuse   (19)
       
19 (18) Pedicels and rhachis internodes with a translucent or balsamiferous median line   Bothriochloa
+ Pedicels and rhachis internodes solid (or if shallowly grooved see Dichanthium annulatum x Bothriochloa bladhii)   Dichanthium
       
20 (17) Homogamous spikelets all pedicelled; sessile spikelet solitary (rarely a second present) with 2 pedicelled spikelets; raceme deciduous below the homogamous spikelets, these and the sessile spikelets falling as a unit   Iseilema
+ Homogamous spikelets sessile, persistent; sessile spikelets 1-4, each with its pedicelled attendant, the sessile spikelets separately deciduous   Themeda
       
21 (16) Racemes 1-noded, reduced to three heteromorphous spikelets enclosed in a boat-shaped spathe   Apluda
+ Racemes many-noded, not contained in a boat-shaped spathe   (22)
       
22 (21) Lower glume of sessile spikelet transversely rugose; pedicelled spikelet represented only by a curved pedicel   Thelepogon
+ Lower glume of sessile spikelet smooth, rarely rugose but then the pedicelled spikelet well developed   (23)
       
23 (22) Callus of sessile spikelet applied obliquely to the apex of the internode with its tip free, usually acute to pungent; lower glume of sessile spikelet convexly rounded on the back without keels; internodes and pedicels linear   Hyparrhenia
+ Callus of sessile spikelet inserted into the crateriform or cupuliform tip of the internode, at least the rim of the internode lapping over and concealing the tip of the callus; lower glume of sessile spikelet 2 -keeled or with the margins sharply inflexed, and usually depressed between the keels, rarely the keels rounded but then the glume deeply grooved between them   (24)
       
24 (23) Lower floret of sessile spikelet male or with a well-developed palea   (25)
+ Lower floret of sessile spikelet barren and reduced to a lemma   (26)
       
25 (24) Racemes paired or digitate, rarely solitary but then the upper glume awnless   Ischaemum
+ Racemes solitary; glumes conspicuously winged, the upper awned   Sehima
       
26 (24) Racemes solitary; lower glume of sessile spikelet convex on the back, the keels lateral or frontal with several intercarinal nerves   Schizachyrium
+ Racemes paired or digitate, rarely solitary but then with the lower glume of sessile spikelet concave and nerveless between the keels   (27)
       
27 (26) Racemes deflexed at maturity, borne upon subequal flattened raceme-bases, seldom exceeding the spatheole in length; leaves aromatic   Cymbopogon
+ Racemes not deflexed, borne upon unequal ± terete raceme bases; leaves not aromatic   Andropogon
       
28 (2) Pedicels distinct   (29)
+ Pedicels fused to the internodes, rarely wanting   (32)
       
29 (28) Jointing of racemes oblique   Elionurus
+ Jointing of racemes transverse   (30)
       
30 (29) Raceme solitary, cylindrical, glabrous   Mnesithea
+ Racemes solitary or subdigitate, ± flattened, glabrous or silky-villous   (31)
       
31 (30) Racemes subdigitate (rarely solitary), glabrous   Phacelurus
+ Raceme solitary, silky-villous   Lasiurus
       
32 (28) Lower glume of sessile spikelet rough   Hackelochloa
+ Lower glume of sessile spikelet smooth   (33)
       
33 (32) Racemes dorsally compressed, tough   Hemarthria
+ Racemes cylindrical, fragile   Rottboellia
       
34 (1) Female spikelets completely enclosed in a metamorphosed leaf-sheath (cupule) which takes the form of a spherical or cylindrical osseous or ivory bead -like structure   Coix
+ Female spikelets not enclosed in a cupule as above   (35)
       
35 (34) Inflorescence with female spikelets in crowded, longitudinal rows on a very thick spongy axis; male spikelets in ample terminal panicles   Zea
+ Inflorescence consisting of male racemes with 1-several female spikelets at the base, these each partially enclosed by the thickly coriaceous lower glume   Chionachne

  • List of lower taxa


     

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  • FOC22_28_Andropogoneae.pdf
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