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Alliance II. ACANTHALES. 
Essential Character. — Flowers unsymmetrical, usually didynamous. Seeds adhering 
to hard hook-like processes of the placenta. Albumen 0. Calyx 4-5-leaved, remarkably 
imbricated, as if in more whorls than one ; often enveloped in large bracts. 
Order CCXIII. ACANTHACE.^, The Justicia Tribe. 
Acanthi, Juss. Gen. 102. (1789). — Acanthace^e, R. Brown Prodr. 472. (1810) ; Link 
Handb. 1. 500. (1829) a sect, of Personatae ; Neesab Esenbeck in Wall. Plant. As. 
rar.3. 70. (1832). 
Essential Character. — Calyx 4- or 5-divided, usually 5-leav.ed, equal or unequal, 
generally very much imbricated, occasionally multifid, or entire and obsolete, persistent. 
Corolla monopetalous, hypogynous, bearing the stamens, mostly irregular ; the limb ringent 
or 2-lipped (the lower lip overlapping the upper in aestivation), occasionally 1-lipped, some- 
times nearly equal, deciduous. Stamens mostly 2, both bearing anthers ; sometimes 4, 
didynamous, the shorter ones being sometimes sterile ; anthers either 2-celled, their cells 
being inserted equally or unequally, or 1 -celled, opening lengthwise. Ovary seated in a 
disk, 2-celled, the cells either 2-or many-seeded ; style 1 ; stigma 2-lobed, rarely undivided. 
Capsule 2-celled, the cells 2- or many-seeded, by abortion sometimes becoming 1 -seeded, 
bursting elastically with 2 valves. Dissepiment opposite the valves, separable into two 
pieces through the axis (the middle being sometimes open) ; these pieces attached to the 
valves, sometimes separating from them with elasticity ; entire, or occasionally sponta- 
neously separating in two, their inner edge bearing the seeds. Seeds roundish, hanging by 
ascending processes of the placenta, hard, cup-shaped, or usually hooked ; testa loose ; 
albumen none ; embryo curved or straight ; cotyledons large, roundish ; radicle taper, 
descending, and at the same time centripetal, curved, or straight ; plumula inconspicuous. 
— Herbaceous plants or shrubs, chiefiy tropical ; their hairs, if they have any, simple, occa- 
sionally capitate, very rarely stellate. Leaves opposite, rarely in fours, without stipules, 
simple, undivided, entire, or serrated ; rarely sinuate, or having a tendency to become 
lobed. Inflorescence terminal, or axillary, in spikes, racemes, fascicles, or panicles ; the 
flowers sometimes even solitary. Flowers usually opposite in the spikes, sometimes alter- 
nate, with 3 bracts, of which the lateral are now and then deficient; these bracts some- 
times large and leafy, and enclosing a diminished calyx, which is occasionally obsolete. R. 
Br. chiefly. 
Anomalies. A singular depauperation of the calyx takes place in the genera Thun- 
bergia, Mendozia, and Clistax, in which that organ is reduced sometimes to a mere obso- 
lete ring, its place being supplied by bracts. Mendozia is also remarkable for its fruit 
being a 1- seeded drupe, with crumpled chrysaloid cotyledons. 
Affinities. In habit these approach Scrophulariaceae, from which their 
want of albumen, elastically dehiscing fruit, the hard processes of the dissepi- 
ment, and the much imbricated calyx, distinguish them ; with Bignoniacese they 
agree so nearly in character, that they may be said to differ in nothing but their 
seeds not being winged, and their imbricated calyx, for the processes of the seeds 
are sometimes absent ; generally, however, their flowers being intermixed with 
imbricated bracts, their many-leaved imbricated calyx, and their herbaceous 
habit, point them out sufficiently. To Pedaliacese they approach in character, 
but are at once known by their 2-celled ovary and peculiar habit. Von Mar- 
tins remarks (Nov. Gen. et Sp. 3. 27.) that the didynamy of Acanthacese is fre- 
quently different from that of Scrophulariaceae in the posterior pair of stamens 
being the longest, and the anterior pair shortest. Recently the order has been 
elaborately remodelled by Nees Von Esenbeck, to whose excellent memoir in 
the place above quoted all Botanists should have recourse. Among other cu- 
rious speculations in this remarkable treatise is one that the irregularity so 
common in the anthers of this order is connected with a general tendency to 
unequal dichotomy, which is more particularly indicated by one of the oppo- 
site leaves being unequal, by the bases of the leaves being frequently oblique. 
