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Acanthaceae
Acanthus Family
Introduction
• Perennial herbs, vines
or occasionally shrubs
• Sometimes armed
Leaves
• Simple
• Usually entire
• Oppositely arranged
(decussate)
• Exstipulate (no stipules)
Inflorescence
• Determinate
(inflorescence in which
the terminal or central
flower opens first)
– Cymose
– Often appearing
racemose, paniculate, or
spicate
• Flower sometimes
solitary
Flowers
• Zygomorphic
(bilaterally symmetrical)
• Perfect
• Hypogenous (superior
ovary)
• Showy
• With nectariferous disc
• Often subtended by
conspicuous bracts
Calyx
• Synsepalous (sepals
fused together)with 5
or sometimes 4 lobes
• Convolute (overlapping)
or imbricate
(overlapping like
shingles)
• Persistent
Corolla
• Sympetalous with 5
lobes
• Usually bilabiate
(having 2 lips)
• Imbricate or convolute
• Variously colored
Androecium
• Usually 4 stamens
• Didynamous
– If didynamous then 1
staminode present
• Sometimes reduced to
2 stamens and 2
staminodes
• Epipetalous
• Filaments distinct or
coherent in pairs
Androecium
• Anthers more or less
basifixed
• 2- or 1-locular
– Locules unequal and at
different levels
• Sometimes spurred
and/or hairy
• Sometimes with
prominent connective
• Dehiscing longitudinally
Gynoecium
• Of 1 pistil
– 2-carpellate
• Superior ovary
– 2-locular
• 1 style
– Slender
– Filiform
• Stigmas 1-2
– Funnelform or 2-lobed
– Often with a reduced
posterior lobe
Gynoecium
• Ovules 2-10 in 2 rows in
each locule with
modified funicle
• Placentation axile
Fruit
• An elastic loculicidal
capsule
– With 2 recurving valves
• Seeds usually flat
– Supported by small
hook-like projections
• Retinacula
• Jaculators
Fruit
• With very thin,
mucilaginous (slimy)
seed coat
• Endosperm usually
absent
• Embryo large
– Curved, bent, sometimes
straight
Representative
Genera
Anisacanthus quadrifidus var. wrightii
Flame acanthus
• Small, bushy shrub 61-122 cm
tall
• Soft hairs line the stems from
between one pair of leaves to
the axils of the next lower leaf
pair
• Lanceolate leaves up to 5.7 cm
long, with petiole; hairs line the
midrib and petiole
• Orange flowers about 3.8 cm
long and in terminal spikes
Dyschoriste linearis
Snake herb
• Rather stiffly upright, coarsely and
stiffly hairy perennial, 18-30 cm tall;
stems 4-angled, few to several,
usually unbranched
• Leaves 16-50 mm long, opposite,
stalkless, rather rigid; margins fringed
with hairs
• Flowers 16-35 mm long, bluishpurple or lavender, dark-spotted in
throat, hairy outside, somewhat
tubular, 2-lipped; upper lip unlobed;
lower lip deeply 3-lobed; stalkless,
from upper leaf axils
Justicia americana
American water-willow
• Upright, smooth perennial herb to 76 cm;
stems angled, slender, branched in upper
portion, usually rooting in lower portion
• Leaves 7.6-15 cm long, narrow, opposite,
stalkless or almost so, narrowed at both
ends; margins entire
• Flowers 10-13 mm long, white or
occasionally violet, dotted with purple, 2lipped; upper lip notched or 2-lobed,
turned backward; lower lip deeply 3lobed, occasionally turned under; flowers
few, in cluster at tip of long stalk from
leaf axils
Ruellia drummondiana
Drummond's ruellia
• Coarse erect plant, 30-91
cm tall; stem 4-angled
covered with short, stiff,
slightly rough hairs
• Leaves 5-15 cm long with
undulating margins; on
petioles 1.3-2.5 cm long;
usually dark green on the
upper surface and pale
green on the lower surface
• Cluster of 2-7 flowers grow
from leaf axils; purple to
light purple; 3.8 cm long
Ruellia humilis
Fringeleaf wild petunia
• Upright to somewhat sprawling, clumped,
rather stout, conspicuously hairy perennial up
to 81 cm tall; stems usually several in a clump,
prominently 4-angled, branched; branches
slender often lying on the ground
• Leaves to 8 cm long, 4.5 cm wide, opposite,
essentially stalkless, somewhat crowded on
the stem; blade leathery, blunt or wedgeshaped at base and extending onto stalk, blunt
or sharp-pointed at tip, densely hairy on veins
and margins
• Flowers 5-8 cm long to 2 cm wide, lavender to
purplish-blue, usually with darker markings in
the throat, trumpet-shaped, deeply 5-lobed at
the rim; flowers few in clusters from middle
and upper leaf axils
Ruellia nudiflora
Violet ruellia
• Upright to semi-sprawling perennial to
71 cm tall from a somewhat woody
base; stem solitary, branching in upper
portion; plant densely hairy when young
becoming almost entirely smooth with
age
• Leaves generally 6 cm long and 3 cm
wide, opposite, stalked; blade graygreen, prominently net-veined on lower
surface; margins curled or wavy-toothed
• Flowers 55 mm long, 38 mm wide,
lavender to purple, trumpet-shaped,
deeply 5-lobed at rim, conspicuously
curved, falling from plant in early
afternoon
Ruellia occidentalis
Western wild petunia
• Duration: Perennial
Habit: Herb
Leaf Complexity: Simple
Leaf Shape: Ovate
Leaf Venation: Pinnately
Veined
Leaf Pubescence:
Puberulent
Leaf Margin: Undulate
Leaf Apex: Rounded
Leaf Base: Rounded
Flower Size: 7 cm long
Sepals: calyx lobes linearattenuate
Size Class: 1-3 ft.
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Nightshade
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