CXXII. — PLUMBAGINACEAE.
This is a small order and one with which the Indian Botanist has but little trouble, the Indian species being very few. Of ten genera, referred to the order, only three have Indian representatives, and among them only furnish four species. Scinde and Cabul have several more, some of which it seems probable may be found eastward of the Indus but as yet, so far as I can discover, none of them have been found in our North Western provinces. The Scinde and Cabul ones belong to that most difficult genus, Statice, for specimens of one species of which I am indebted to Mr. Stocks. The order, being thus sparingly distributed in India, need not occupy much of our time or space. A most elaborate Monograph by M. E. Boissier has recently been published in De Candolle's Prodromus, but which, so far as this work is con- cerned, seems unnecessarily detailed and copious, especially in the character of the order which occupies three pages of that work.
{{sc|Character of the Order.INDIAN Calyx tubular, persistent, sometimes coloured, corolla (of very thin texture) monopetalous, with a narrow tube, or composed of 5 petals, which have a long narrow claw. Stamens definite, opposite the petals, in the monopetalous species hypogv- nous [in Plumbago seated on the very bottom of the corolla but not truly hypogynous], in the polypetalous rising from the petals. Ovary superior composed of 5 (or 3 or 4) valvate carpels, 1-celled, 1-seeded; ovule anatropal, pendulous from the point of an umbelical cord arising from the bottom of the cavity ; styles 5 ! seldom 3 or 4 ; stigmas the same number. Fruit a nearly indehiscent utricle. Seed inverted with a rather small quantity of mealy albu- men ; testa simple; embryo straight ; radicle superior.
Affinities. On this point considerable difference of opinion for some time existed, and of a kind suited to give rise to a curious question, one, apparently, easily answered, but in reality a very difficult one, namely, how to distinguish the calyx from the corolla. Jussieu, and afterwards De Candolle, considered the part here called the calyx a kind of involucrum, and the petals as a perianth or calyx. Mr. Brown adopted the opposite opinion and pronounced the so called involucrum and calyx a real calyx and corolla, not apparent, and consequently that these plants did not belong to the monochlamedious class. Admitting that this view is correct, that the stamens are opposite the petals, that the ovary has 5 carpels, but is only 1-celled with a central free placenta (for such, I presume, the long filiform fuuiculous from which the ovule is suspended may be considered), then the relationships of the order seem evi- dently to lie in my first group (see page 127). But if, on the other hand, Jussieu's idea is adopted, which views the corolla as a calyx, then the order is transferred to a different class and may indeed be viewed as the transition order. In regard to the position of the stamens, which must have some weight in deciding this question, I find that, in Statice, they are inserted on the petals as in the Myrsineous group, but in Plumbago, they have a glandular enlargement at the base of the filaments by which they cohere, forming a ring round the base of the ovary, but are perigynous, that is inserted on the base of the part called corolla, not hypogynous, and have the filaments opposite the lobes. These facts go far to throw doubt on the correctness of Mr. Brown's opinion, and to leave this still an open question. Lindley remarks that they are distinguished from all the monopetalous orders by their plicate calyx, and Brown commences his definition of Plumbago with the words, "calyx plicatus." As applied to P. Zeylanica, I do not understand the meaning of the term. Fresh flowering specimens are now before me, but they present neither plait nor fold, I therefore attach less weight to that mark of distinction than to the very unusual one of the ovule being suspended from the apex of a cord which rises from the base of the cell, a peculiarity, to the best of my recollection, not elsewhere met within this sub-class, and forming an admirable point of structure by which to associate, as one family, nearly all plants in which it occurs.
Geographical Distribution. "In toto orbe terrarum occurrunt C such are the few but comprehensive words of the M. Boissier in regard to their distribution in general.
