ILLUSTRATIONS OF INDIAN BOTANY-
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cell, attached to cup-shaped, subulate or hooked processes (retinacula) of the placenta ; testa coriaceous, fibrous or loose, often tuberculate, sometimes pilose; albumen none; embryo curved or straight ; cotyledons large, roundish ; radicle taper, descending and at the same time centripetal, curved or straight. — Herbaceous plants or shrubs ; stem and branches nodosely jointed ; hairs when present simple, capitate or jointed ; leaves often beset with white hair- like lines (lineoles) under the epidermis which, after breaking the cutula, effervesce on the appli- cation of an acid. Leaves opposite or, rarely, in fours, exstipulate, entire or serrated, rarely showing a tendency to become lobed, sometimes in unequal pairs. Inflorescence terminal or axillary, in spikes, racemes, fascicles, or panicles. Flowers usually opposite on the spikes, or sometimes alternate, furnished with 3 bracts, of which the lateral pair are now and then deficient; bracts often large and foliaceous, and then the calyx is usually much diminished in size. — This large and complex order is essentially distinguished from all others by its elastic, 2-valved capsules and retinacula or placentary processes to which the seeds are so generally attached : for it may truly be said that by these alone it is separated from all others, though it must at the same time be admitted they are not altogether without exceptions ; these however are so few as hardly to militate against the general rule.
Affinities. I have placed this order next Pedaliacece (at the end of the Bignonal group) as forming, through Sesamum, an almost direct transition to that group of orders. Acanthacece certainly want the spurious partition which divides the 2-celled ovary and capsule of Sesamum into a 4-celled fruit ; and Sesamum is, in like manner, deficient in the retinacula, so remarkable in this family, but otherwise the capsules are very similar ; in both the dehiscence is contrary or through the axis of the septum which remains attached partly to both valves; in both the seed are arranged in two rows in the cells and are exalbuminous ; and, as regards the flowers, it is almost impossible to draw distinctions in a family where almost every form and variation are to be met with, but in both they are irregular. Pedaliacece and Acanthacece being thus closely allied, it follows that the nearest affinities of Acanthacece are Bignoniacece, on the one side, and Pedaliacece on the other, to which I would add Schrebereaz, which I now view as the type of an order, but for the present reduce to a sub-order appertaining to this group. Formerly Acanthacece were considered rather nearly allied to Scrophulnriacece, but from which they are removed by their parietal, not axile, placentation and exalbuminous seed. But though these two great orders of irregular flowered plants are thus kept distinct by characters, they occa- sionally so far interblend in habit that they might, but for the fructification, be mistaken for each other. Hence, having the characters of the Bignonal set of orders strongly marked, and to some extent the habit of Scrophulnriacece, they seem to occupy a suitable station here, as form- ing the connecting link between them.
Geographical Distribution. This is a, peculiarly, tropical order, for, though not con- fined to the tropics, they rarely extend beyond the warm regions bordering them. Two or three are found in Southern Europe and North America, and some in Australia. In India, tropical America, and Africa, they abound. In the Indian peninsula the proportion of Acanthacece equals or perhaps exceeds, in the number of its species, most other dicotyledonous orders ; Legumenosce, and perhaps Composites, being, I fancy, almost the only ones by which it is, to any considerable extent, exceeded. As regards Southern India, I suspect species of the Acanthacece are about as numerous as those of Compositce. They are found in all soils and situations, wet and dry, in shade and exposed to the strongest light, and equally on the sea shore and tops of our highest mountains : they are numerous on the highest ranges of the Neilgherries. Their forms are equally variable, ranging from very minute herbs up to moderate sized shrubs.
Properties and Uses. These are not important. Some, such as Andrographis paniculata (Justicia Lin), or Creat, possess medicinal properties of considerable energy, the plant named being intensely bitter and as such used, either singly or in combination, as a tonic. Some are used in the arts as dyes, and several are most deservedly admitted into the parterre, as affording most ornamental subjects for the garden and flower border. But more generally they can at best be designated as weeds, having neither use nor beauty to recommend them to our attention
