XXX—OLACINEAE.
A small order, nearly confined to the tropics, consisting for the most part of shrubs or small trees, often climbing or diffuse, more rarely erect, and armed with spines. The leaves are exstipulate, alternate, simple, petioled, undivided and entire : more rarely as in Balanites,, bifoliolate. The flowers are bisexual, or occasionally, by abortion, polygamous, or dioicous, small, axillary, racemose.
Calyx small, either entire and slightly toothed, or 5 sepaled, often, when entire, becoming enlarged with the fruit. Petals 3-5-6, either separate or adhering in pairs ; aestivation valvate. Stamens 3 10, either all fertile, or with alternate sterile ones, hypogynous, often variously united with the petals, either opposite to them when the flowers are symmetrical, or wholly or partially alternate, when unsymmetrical : filaments compressed: anthers oblong, bursting longitudinally. Ovary 1-5 celled, with pendulous ovules. Fruit drupacious indehiscent, occasionally surrounded by the enlarged calyx, 1-celled, 1 -seeded. Seed usually pendulous. Albumen copious,, fleshy. Embryo with the radicle next the hilum.
In Olax, the fertile stamens alternate with the petals and unite them by pairs; in Ximenia, and also Opilia, they are opposite the petals, not the sepals in the latter, as stated, through an oversight of the authors, in the Flora Senegambiœ, who seem to have overlooked the minute calyx of that genus. In Gomphandra Wall, (list No. 3718) which seems nearly allied to Stemonoous, Blume, the stamens equal the petals, and alternate with them 3 while the flowers are usually unisexual by abortion.
Affinities. These are very uncertain, most authors however agree in adopting DeCandolle's arrangement, and place them near Aurantiaceœ, with which they unquestionably have many points of affinity. But on the other hand, the character of the seed of Olacineœ is so totally at variance with what we find in Aurantiaceœ, that it is not easy to reconcile one's self to view that as a natural arrangement, which places plants differing so widely, in so essential an organ as the seed, side by side. Mr. Brown takes a very different view of their structure. He considers them apetalous, viewing the organs called petals by other authors as sepals, and their sepals as an involucrum. According to this view of its structure, the order should occupy a place near Santalaceœ and Thymaleœ, with which it agrees in the character of its seed. In opposition to this view, it may be stated on the one side, that Balanites which is now referred to this order has distinct sepals and petals, and on the other, that Ternstraemiaceae, and especially the genus Ternstrœmiahas the embryo in the midst of a copious albumen some-what similar to what we find in Opilia, and Balanites. For these reasons, added to the similarity in various points between the flowers of Ximenia and Balanites, to those of the Aurantiaceœ, I do not see that, in the present state of our knowledge of the order, we can assign it a more suitable place than that which it now occupies, between these two orders, the relationship of which seems generally admitted.
Geographical Distribution. As already remarked, the order consists almost entirely of tropical shrubs or small trees. Though few in number they have a wide range, being met with with in, or on the confines of the tropics in Asia, Africa, America, and Australia.
In continental India 5 genera are found, and one more from Java, altogether 6 of the 12 genera referred to the order. The continental ones are Olax, Gompandra, Opilia, Ximinia, and Balanites. Olax is also found on the banks of the Congo, while the three last are found in Senegal, and apparently the same species. Ximenia Americana is common to three quarters of the globe. Balanites is equally a native of India and of Africa, and has been well described by Roxburgh under the name of Ximenia Ægyptiaca. Of this genus I possess specimens and drawings, the latter of which will shortly be published in my Icones. The genus-Olax extends from Ceylon northwards to the Himalayas, and from Malabar eastwards to Java, while Spermaxyrum, a genus scarcely distinct, represents it in New Holland. With this almost unlimited range, in respect to longitude in its distribution over the torrid zone, this order can scarcely boast of more than 30 known species, about 20 of which are natives of India and
