Stylosanthes FABACEAE 101 
STYLOSANTHES Sw. 
Herbs or subshrubs. Stipules adnate to lower part of petiole and sheathing the stem, 2-lobed, lobes aristate, 
leaf arising from the sinus. Leaves pinnately 3-foliolate. Inflorescences axillary or terminal, sessile, spicate or 
appearing capitate, 1-many-flowered, of 1-flowered spikes in axils of primary bracts (lowermost in the axil of 
primary leaf); outer bracts sheathing, highly imbricate, stipule-like, 1-3-foliolate; inner bracts ovate, 2-3-fid, 
hyaline, ciliate, persistent. Flowers sessile, each accompanied by a 2° bract and 1-2 hyaline, linear, ciliate 
bracteoles and sometimes by a plumose filiform axis rudiment. Calyx tube long, filiform, pedicel-like; lobes 
5, membranous, ciliate, united at base, upper 4 connate for c. 1/2 their length, obtuse, lower lobe free, narrow, 
acute. Petals and stamens inserted in throat of calyx. Standard obovate or suborbicular, emarginate, shortly 
clawed; wings and keel laterally spurred, pouched; keel incurved. Stamens 5+5, anthers dimorphic, alternately 
long and basifixed, and short and versatile. Ovary subsessile, 2(3)-ovuled; style curved, filiform, persisting on 
fruit, stigma minute. Pod sessile, articulated, lower article often abortive, upper article + obloid, laterally 
compressed, keeled, venation reticulate, apex beaked, often hooked. Seeds ovoid or ellipsoid, compressed. 
A genus of c. 25 species, mostly in South America. Several species have been introduced to Australia for 
pasture improvement and 5 are now naturalised. These 5 are cultivated in the NT and are treated here. Only 
two species have become well established members of the flora in the DR, viz. S. humilis and S. hamata. The 
generic description is taken from Reynolds (1990). 
1. Stylar hook on pod >4 mm long ou... ceeeeeeseeeeeeeeeteees 
1. Stylar hook on pod absent or <2 mm long 
2% stipules bristl yp tescccrsscccrstetesticsstslsortersesttierstte 
2. Stipules glabrous or alMOSt SO... seeeeseessseseseeeneenenees 
Rn eee 2 
3 
S. humilis 
S. hamata 
3. Terminal segment of leaf rachis <1 mm long, leaves appearing digitate; 
leaflets:to 40 mm) long metmeresssrceserrrestitttttitecrtts: 
S. guianensis 
3. Terminal segment of leaf rachis >1 mm long; leaflets to 17 mm JON .......ccceeseseeeeeeeeees 4 
4. — Stylar hook 1.5-2 mm long; pod with long hairs ........ 
4. Stylar hook <1 mm long; pod with short papillose hairs 
*S. guianensis (Aublet) Sw. 
Semiprostrate, short lived perennial to 50 cm 
high. Vegetative parts pubescent with soft patent 
hairs and glandular yellow or red bristles. Stipules 
to 15 mm long. Leaves appearing digitately 
3- foliolate with a terminal segment <1 mm long; 
rachis 3-8 mm long; leaflets narrowly elliptic, 14-40 
mm long, 4-9 mm wide, L/W 2.9-6.6, the 3° venation 
below often resinous. Flowers 5-10 mm long. Pod 
l-articled, 3.5-3.8 mm long, smooth, glabrous, thin 
walled with obscure venation; residual style <1 mm 
long. Seed pale brown. Flowering and fruiting: May 
- July. Fig. 29 Stylo 
In Australia in WA, Qld and NT. Uncommon in the 
NT and DR, on disturbed sites. 
*S. hamata (L.) Taub. 
Short lived decumbent perennial to 50 cm high. 
Stems with a band of patent fine hyaline hairs on 
one side, otherwise glabrous. Stipules to 17 mm 
long, mostly glabrous. Rachis to basal leaflets 3-6 
mm, 5-10 mm overall; /eaflets narrowly elliptic, 
S. scabra 
ee ee i areiistirittess: S. viscosa 
10-28 mm long, 2-5 mm wide, L/W 3.5-6.3. Bracts 
of the inflorescence ciliate. Flowers 7-10 mm 
long. Pod 1-2-articled, 3-6 mm long, articles 3-4 
mm long, terminal stylar hook c. 4 mm long. 
Seed reddish brown. Flowering and fruiting: May - 
Nov. Fig. 29 Verano 
In WA, Qld and in the NT in the Top End and DR. 
Common on disturbed sites around settlements. 
*S. humilis Kunth 
Suffruticose prostrate or erect annuals. Stems 
with a line of minute, glandular based curved 
hairs on one side; long, patent, tubercular based 
bristles on most parts, especially the stipules 
and floral bracts. Stipules to 10 mm long. 
Leaflets narrowly lanceolate or narrowly elliptic, 
5-24 mm long, 1.8-5 mm wide, L/W 2.5-7.5. Flowers 
5-8 mm long. Pod c. 3 mm long, terminal stylar 
hook 4-6 mm long, thinly sericeous. Seed 
yellow-brown. Flowering and fruiting: Apr - July. 
Fig. 29 Townsville Stylo (TS) 
