Page:Illustrations of Indian Botany, Vol. 2.djvu/351

ILLUSTRATIONS OF INDIAN BOTANY.

183 of a spurious partition, or membranous extension or band, which afterwards thickens, becoming, in the accompanying species, firm, coriaceous and straplike, but in others round, thick and spongy, bearing on its sides the seed. Some however are truly two-celled.

Calyx lobed or entire, sometimes spathaceous. Corolla monopetalous, hypogynous, deciduous, irregular, 4-5-lobed or sub-bilabiate, lobes imbricating in aestivation. Stamens usually 4, fertile, didynamous, with a sterile filament, sometimes all fertile ; anthers 2-celled, cells parallel and contiguous or separate and diverging, opening longitudi- nally. Disk glandulose, tumid, embracing the base of the ovary. Ovary 2- rarely 1-celled, ovules several or numerous, attached to lateral placentae usually united in the axis by a short process which, with the thickened placentae, afterwards becomes the spongy partition. Style filiform, stigma bilamellate or bifid, lamellae anticous and posticous. Capsule 2-valved, 2-celled, often long, compressed, sometimes spuriously 4-celled, the septum either parallel to the valves, or contrary to them, finally separating and bearing the seeds. Seeds transverse, compressed, winged, exalbuminous ; embryo straight next the hilum, cotyledons flat, foliaceous or fleshy. — Trees or shurbs, stems erect, scandent, or twining. Leaves opposite, sometimes simple, usually compound, the petiol sometimes produced into a tendril. Stipules none, but sometimes re- placed by accessory leaflets. Inflorescence usually panicled or racemose.

As regards the flowers this order is nearly allied to Pedaliacece, Gesneriacece, Acanthacece, and Scrophulariacece, but is kept distinct from all by its winged seed, provided the section Crescentiece, which De Candolle retains, is separated to form a new order, a view in which Botanists now generally coincide, as its retention may be said to break down the essential character of the order. Much stress is laid on the axile position of the placentae, which Lindley observes "is an indispensable character of this natural order," but immediately goes on to observe that "the genus Eccremocarpus, however, appears to be an exception, its placentae being strictly parietal at the time of the expansion of the flower" and, further, that he long since stated that the placentation of Bignonia radicans is originally of the same nature, the difference between them consisting in the 2 placentae of the latter meeting in the axis and uniting there, while those of Eccremocarpus never touch in the middle. The same seems to be the case in the species here figured ( Spathodea adenophylla ), and doubtless will be found in many others, when all have been examined at a sufficiently early stage. I have remarked a similar structure in several species of Acanthacece, the inflexed valves of whieh do not quite meet until after the fall of the flower, though they also are said to have axile placentation. But indeed the difference between the fruit of Bignoniacece and Acanthacece, at least as I understand them, is not so great as, at first sight, one might be led to suppose, and neither have, strictly speaking, axile placentae, such as in Scrophulariacece. The structure of the ovary in both families is nearly the same, and both have bivalved, 2-celled, dehiscent capsules. The essential difference, therefore, exclusive of habit, is found in the spurious partition of Bignoniacece, and in the mode of dehiscence of the capsule in the two families. In the former (Bignoniaceae) it is either septicidal or loculicidal but without elasticity ; in the latter it is always loculicidal. In other words, in the tribe Eubignoniacece the dehiscence takes place in the line of the placentae, equivalent to septicidal ; the spurious partition, on the sides of which the seeds lie, at the same time separating from the valves, is found loose within the capsule : the septum is then said to be parallel to the valves. In the sub-tribe Catalpece it takes place along the middle or dorsum of the carpels, that is, loculicidally ; the partition is then said to be contrary or with its edges opposite the middle of the valves, which valves, in this case, are each made up of two half carpels cohering along their placentary margins. This is precisely what takes place in Acanthacece, with this difference, that in Acanthaceae there is no free, spurious partition, but the seed are attached to persistent placentary processes, and the valves usually separate with elasticity. The affinity, therefore, between Acanthacece and the sub-tribe Catalpece is very close. The affinity between Bignoniacece and Scrophulariacece, which Lindley also places in his Bignonal Alliance, is not so close, for though they associate as well as regards the flower, the placentation differs in being decidedly axile and the seed albuminous, neither of which is truly the cage in Bignoniaceae or Acanthaceae.