CYTOTAXONOMIC STUDIES IN THE LOGANIACEAE. I. CHROMOSOME NUMBERS AND PHYLOGENY IN THE LOGANIACEAE

THE FAMILY Loganiaceae has long been considered an artificial group and there has been marked disagreement over intergeneric relationships and over the admission of certain genera into the family. For the purpose of obtaining further evidence on these problems a survey of the chromosome numbers of the family was undertaken. The majority of the Loganiaceae are woody plants-trees, shrubs and lianas-but a few are herbs. In distribution the family is tropical and warm temperate, in both the New and the Old World. Twenty per cent of the total number of genera occur in both hemispheres, 30 per cent in the Americas and the remaining 50 per cent in the Old World only. The 2 largest genera-Strychnos, with about 200 species (Krukoff and Monachino, 1942) and Buddleja, of probably about 150 species (Smith, 1937)-are cosmopolitan in the tropics. However, almost half of the genera are small and restricted in range. The Loganiaceae is characterized by usually bisexual, regular 4or 5-parted flowers. The corolla is gamopetalous, funnel-form, campanulate or rotate. The aestivation is valvate, imbricate or contorted. The stamens are equal in number to the corolla lobes; the filaments, with few exceptions, are attached to the corolla tube. The ovary is superior, typically of 2 carpels, less commonly of 1 or several or of 2 incompletely united carpels. Ovules are numerous, rarely only 1, amphitropous or anatropous; placentation axile. A disc is absent or only slightly developed. The fruit is a capsule, berry or drupe. With few exceptions (a few species of Buddleja) the leaf arrangement is opposite. Leaves are entire or finely toothed. Stipules or stipular lines characterize the family. The Loganiaceae is recognized by all authors as a member of the order Contortae (Gentianales). In this order are included, as well, the families Gentianaceae, Apocynaceae and Asclepiadaceae and occasionally one or more of the Oleaceae, Menvanthaceae and Salvadoraceae. Some genera of the Loganiaceae show affinities to the Apocvnaceae, Rubiaceae and Scrophulariaccae. Engler (Coulter and Chamberlain, 1903) has suggested that the Loganiaceae is older than the other families of the Contortae and may contain the descendants of the line ancestral to the Contortae and Rubiales. Apparently Robert Brown (Lindley, 1846, p. 602) was the first to establish a family named 'Received for publication Mav 23, 1947. Appreciation is expressed to Dr. 0. E. White under whose direction this investigation was carried out and to Dr. H. A. Senn, Division of Botany and Plant Pathology, Dept. of Agriculture, Ottawa, Canada, who made available much of the material studied and who read and criticized the manuscript. Loganiaceae. Previously the genera of the present family had been distributed among related families. The Loganiaceae of Brown (l.c.), of A. P. de Candolle (Prodromus, 1824-73), of Endlicher (183640) and of Lindley (1846) did not include all the genera considered members of the modern family, several genera being placed in the Scrophulariaceae (Buddleja), Rubiaceae (Polypremum) and Apocynaceae (Gelsemium) and groups of others were regarded as families independent of the Loganiaceae. Bureau (1856) revised the Loganiaceae and removed from it many genera of uncertain relationships: Gelsemium, to Apocynaceae; Fagraea, Potalia, and Anthocleista, to Gentianaceae; Nuxia, to Scrophulariaceae; Mitreola, Mitrasacme, Polypremum and Sykesia (Gaertnera) to Rubiaceae. He believed that the eleven genera left in the Loganiaceae constituted a natural group. While recognizing the artificial nature of the family, Bentham (1857) retained these disputed genera. Using the same systematic characters employed in classifying the Rubiaceae, he divided the thirty-four genera among four tribes which, on the basis of ovary, fruit and seed characters parallel those of the Rubiaceae. The later system of Bentham and Hooker (1873-76) differed from that of Bentham in the intergeneric relationships. Thirty genera were distributed among three tribes on the basis of corolla and style structure and the nature of the fruit. The system of Solereder (1895, 1897; Pilger, 1907) employed different morphologic criteriathe anatomical structure of stem and leaf. In the Loganioideae-a subfamily characterized by entire leaves, the absence of glandular hairs, a superficial development of cork and the presence of intraxylary phloem-were twenty-two genera. In the case of the subfamily Buddleioideae, the leaves were toothed, glandular hairs occurred on leaves and young stems, cork originated in the pericycle and intraxylary phloem was absent. This subfamilv contained nine valid genera, including Buddleja and six closely related smaller genera. Wettstein (1935) raised each subfamily to family rank, as the Loganiaceae and Buddleiaceae. Hallier (1901) advocated radical changes. He referred the Gelsemieae Solered. and Desfontainia to the Oleaceae and incorporated the Buddleioideae Solered. with the Verbenaceae. The remainder of the Loganioideae forms a family between the Apocynaceae and Rubiaceae. Klett (1924) proposed a further system reminiscent of that of Bentham (1857). He retained the genera recognized by Bentham and Hooker and by Solereder and divided them among two subfamilies, Loganioideae and Strychnoideae, on the basis of fruit character.