A monograph of the genus Polhillia (Genisteae: Fabaceae)
Author
du Preez, B.
Author
Dreyer, L. L.
Author
Stirton, C. H.
Author
Muasya, A. M.
text
South African Journal of Botany
2021
2021-05-31
138
156
183
http://dx.doi.org/10.1016/j.sajb.2020.12.022
journal article
10.1016/j.sajb.2020.12.022
1727-9321
10496862
9.
Polhillia pallens
C.H.Stirt.
(
Fig. 18
), S Afr. J. Bot. 52: 2 (1986).
Type:
South Africa
,
Western Cape
,
3420 (
Bredasdorp
):
3 km
west of
Breede River
mouth on south side of river along access road to
Kontiki
(
—
BD),
22 Feb 1981
,
C.J. Burgers
2633
(
NBG
,
holo
.!;
K
,
PRE
iso
!)
Erect shrubs
1.5
—
2.5 m
tall, loosely branching, sprouting from a woody rootstock.
Branches
greyish-brown, glabrescent, lenticels prominent.
Stipules
1.5
—
3.0 mm long, silvery.
Lea
fl
ets
ellipticaloblong, silvery, adpressed sericeous-canescent, flattened to partially conduplicate, apex acute-obtuse, base acute-attenuate, terminal leaflet 3.5
—
7.0 X 1.0
—
3.0 mm, lateral leaflets 3.0
—
6.5 X 1.0
—
3.0 mm; leaves subsessile.
In
fl
orescence
1
—
2 flowered terminal cluster, subsessile; pedicel up to 2.0 mm long; bract 1.0 mm long, linear.
Flowers
yellow, 10.0
—
11.5 mm
long.
Calyx
4.0
—
4.5 mm
long, yellow-green, sometimes flushed maroon, villous; tube 2.5
—
3.0 mm long; dorsal teeth broadly triangular, 1.5
—
2.0 mm long, fused for less than one third of their length, tips acute-obtuse; ventral teeth triangular, 1.5
—
2.0 mm long, fused to about two thirds the lobe length, spreading, apex acute.
Standard
10.0
—
12.0 mm long, claw linear, 3.0
—
4.0 mm long, lamina broadly ovate, 8.0
—
8.5(
—
10.0) X 10.0
—
13.0 mm, apex emarginate, base cordate, back sericeous except along margin.
Wing petals
9.5
—
11.0 mm long, equal to or slightly longer than keel; claw 3.2
—
4.0 mm long; lamina obliquely-oblong, 7.5
—
8.0(
—
9.0) X 4.0
—
4.5 mm
, pilose along midline, apex rounded-truncate, base broadly auriculate, lunate depression with lamellate sculpturing.
Keel petals
9.0
—
10.5 mm
long, claw
3.5
—
4.5 mm
long, lamina obliquely-oblong, 7.0
—
8.0 X
3.8
—
4.5 mm
, pilose along fore half, apex rounded, base triangular-auriculate.
Stamens
basifixed anthers
1.2
—
1.3 mm
long, carinal anther
1.1 mm
long, dorsifixed anthers
0.8 mm
long; staminal tube
6.7
—
8.5 mm
long, unfused portion remaining closely united, tightly arranged around the style.
Pistil
8.2
—
10.2 mm
long; ovary 4.6
—
6.3 X
0.9
—
1.2 mm
, ovules 9; style usually at 70
—
90̊ angle, height of curvature
2.7
—
3.6 mm
, glabrous, except basally.
Fruit
indehiscent, non-plicate, straight, fibrous, sericeous, olive green, 18.0
—
30.0 X 3.0
—
3.5 mm
.
Seed
ovate-reniform, testa olive-green to dark-brown, smooth, 2.0
—
2.9 X
1.8
—
2.2 mm
,
1.6
—
1.9 mm
thick.
Fig. 18.
Composite plate of
Polhillia pallens
. 1
—
Flower front view; 2
—
Flower side view; 3
—
Flower bottom view; 4
—
Wing petal; 5
—
Keel petal; 6
—
Androecium; 7
—
Gynoecium; 8
—
Fruit; 9
—
Close-up of leaf and stipules; 10
—
Habit. Scale bars: 4 mm. Photographs by B. du
Preez
Etymology
The specific epithet
“pallens
” refers to the pale silvery leaves of this species.
Diagnostic characters
Polhillia pallens
is morphologically variable, especially in terms of the shape of the wing and keel petals, but not to an extent that would warrant further recognition of separate taxa. It can be distinguished from
P. curtisiae
and
P. xairuensis
by its adpressed sericeous-canescent, grey leaflets (
versus
densely spreading villous, blue-green leaflets); unfused parts of stamens remaining closely united around the style, style erect at 70
—
90̊ angle (
versus
unfused parts of stamens loosely spread around style, style sub-erect at 45
—
60̊ angle); and by being a tall, sparsely branched shrub of up to
2.5 m
tall (
versus
erect, rounded shrub with dense terminal burst branching, 0.5
—
1.0 m or 1.0
—
1.8 m
tall, respectively).
Distribution, ecology and conservation status
Polhillia pallens
flowers from April to August, with one odd record from February. It was previously broadly circumscribed to include both
P. stirtoniana
and
P. xairuensis
. It is restricted to only a few sites along and near the lower Breede River region (
Fig. 6B
), where it grows in clay soil in Eastern Ruens ^Shale Renosterveld (FRs 13) and in transitional vegetation with Overberg Dune Strandveld (FS 7) on the southern banks of the Breede River (
Mucina and Rutherford, 2006
). This species is threatened by continued agricultural expansion, habitat fragmentation and by severe alien species encroachment at the
type
locality. Some populations are, however, still healthy and plants grow abundantly in at least three of the known sites. The Red Data List status of this species is proposed as Vulnerable (VU A2c;
B
1ab(iii,iv,v)+
B
2ab(iii,iv,v)) following the latest IUCN categories and criteria (
IUCN, 2012
).
Additional specimens examined
South Africa
.
WESTERN CAPE
:
3420 (Bredasdorp):
18 km
south by east of Buffeljachtsrivier (
—
BC),
21 Jun 1968
,
Acocks 23992
(NBG); Road heading due north of Malgas, east of Breede River (
—
BC),
3 Jun 2017
,
B
. du
Preez
289
(BOL),
291
(BOL, PRE),
10 Jul 2018
,
B
. du
Preez
514
(BOL, NBG, PRE); Napkysmond, near Now-I-Know farm (
—
BC),
11 Aug 2017
,
B
. du
Preez
319
(BOL, MO);
3 km
west of Breede River mouth on south side of river along access road to Kontiki (
—
BD),
22 Feb 1981
,
C.J. Burgers 2633 Ex hort.
(NBG);
8 Aug 2017
,
B
. du
Preez
310
(BOL, NBG, PRE); On slope, above and west, of harbour at Witsand (
—
BD),
16 Feb 2005
,
Euston-Brown 700
(NBG); Kloof NW of Mudlark Lodge (
—
BD),
10 Jul 2018
,
B
. du
Preez
512
(BOL, NBG, PRU).