The calyx is composed of 5 sepals, 3 exterior smaller; 2 interior and lateral much longer, and petaloid in appearance, (the wings). The corolla of 5 petals, but generally two of these are not developed, leaving only three, which often adhere at the base ; the anterior one larger than
the others and somewhat boat-shaped; (the keel) the other two are alternate with the upper lateral sepals. Sometimes the whole number is complete, and then the two additional petals which are usually smaller, are placed between the keel and lateral petals, or between the anterior, and large lateral sepals, showing that it is the middle pair, or those alternating with the large petaloid sepals or wings, that are in the ordinary state of the flower suppressed. The keel is sometimes entire, and then, usually with a crest, sometimes 3-lobed, and without a crest,
whence the crest is supposed to be the altered middle lobe of a 3-lobed keel. The stamens below are usually eight, ascending, combined into a tube adhering to the base of the petals ; sometimes 4 and distinct; when combined the tube is split opposite the upper sepal. Anthers clavate, erect, 1-celled, opening by a terminal pore, rarely, by a longitudinal slit. Disk sometimes large and forming a cup round the base of the ovary. Ovary free, compressed, formed of two united carpels, one anterior, and one posterior, usually 2-celled, with the placentae in the axis, but occasionally, 1-celled, from the suppression of one of the cells, and still more rarely, 1-celled, as in Xanthophyllum, with two opposite parietal placenta?. Ovulus solitary, or very rarely, from 2 to 6 in each cell, style simple curved. Fruit loculicidal, sometimes indehiscent. Seeds with a crustacious outer integument, furnished with a carunculus at the base, or an arillus : albumen, usually copious and fleshy ; sometimes reduced to a thin plate, or wanting as in Xanthophyllum : Embryo straight, radical next the hilum, cotyledons usually foliacious. The following further explanation of the nature of the irregularity of the flowers I extract from Dr. Lindley's Natural System of Botany, 2d edition.
"The calyx apparently consists of but three pieces, which are usually green, and like sepals in their common state ; but their real number is 5, the two coloured lateral petal-like bodies, sometimes lying within the apparent sepals, being in reality part of the series of the calyx. The corolla is mostly monopetalous, and, if carefully examined, formed of 3 pieces; namely, the keel and two petals, all soldered together. We have, therefore, an abortion of two petals, according to the laws of alternation : but this is not all; there is not only an abortion of two petals, but of these two which would, if present, be found right and left of the keel. The monopetalous corolla is, therefore, formed by the cohesion of the two posterior and the one anterior petal of a pentapetalous corolla, of which the two lateral petals are suppressed. The keel has an appendage of an anomalous character, called technically a crest, and often consisting of one or even two rows of fringes or divisions, originating not from the margin but from within it, and sometimes cohering in a common membrane at their base. Aug. de St. Hilaire has shown that this crest is nothing more than the deeply-lobed middle segment of a keel, with these lobes in such a state of cohesion that the central lobe is pushed outwards, while the lateral ones cohere by their own margins and with its back. The stamens are only 8, two therefore are suppressed : or in krameria 4, one being suppressed. I may remark, in addition, that the relative position of the fifth sepal and petal respectively, was first indicated by Brown." Denham 31.
Affinities. The opinions of Botanists, have always been much divided in regard to the affinities of this order, and the place it ought to occupy in the natural arrangement of plants Jussieu first placed Polygala among the Monopetalous orders, placing it at the head of his order Pediculares, but afterwards saw reason to change its place, and then ranged it among the Polypetalae. DeCandolle considering it more allied to Violarieae and Droseraceae, placed it after these orders. Bartling has placed it in his class "Rhoeadeae" along with Residaceae, Fumariaceae, Papaveraceae, Cruciferae, and Capparideae. Lindley prefers placing it in his alliance "Acerales" along with Aceraceae (Sycamore's) Sapendaceae, (soap-nuts) and OEsculacece, (horse chesnuts). The following exposition of the affinities of this order, is extracted from his work.
"Polygalaceae are stationed by DeCandolle between Droseraceae and Tremandraceae, and in the immediate vicinity of Violaceae. With the latter they are related on account of their hypogynous stamens, irregular flowers, and cucullate stigma; and with Tremandraceae
