TAXONOMIC STUDY ON THE GENUS LAUROCERASUS TOURN EX DUH.OF CHINA
Lu Ling-ti
1984, 4(4):
37-59.
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The present paper is a preliminary study on Chinese specics of the genus Laurocerasus Tourn. ex Duh., in which Tournefort(Institutiones rei Herbariae 627. t. 403. 1700) first put two species known as Prunus laurceerasus and P. lusitanica, but Linn-aeus transferrd them to the genus Padus Mill. and in Sp Plant. 1753 those species were placed in the rather inclusive genus Prunus L. The systematic position of this genus has been much disputed during more than two centuries after its delimitation. Roemer, Schneider, Komarov and Hutchinson recognized Lcu-rocerasus as an independent genus. In the early part of the 19th century it was reduced by some authors, e. g. Seringe, Rei-chenbach and others to a subgenus or section of the genus Cerasus Mill. Up to the late 19th century to early 20th centuryBentham, Hooker J. D. and Koehne coined an inclusive genus Prunus, therefore the genus Laurocerasus was brought to Prunus as a section or subsection. In later times, Rehder, Kalkman and Vidal considered it to be a subgenus of Prunus. During the course of our writing the Flora of China all the species of Laurocerasus and its allied genera such as Pygeum Gaertn. and Padus Mill. collected from the whole China for the past more than fifty years have been examined. After a detailed investigation of the morphological characters and analysis of geographical distribution of Laurocerasus we accepted the generic concept of Roemer, Schneider and so on, regarded it as an independent genus. The genus Laurocerasus differs from the closely related genus Padus by its leaves usually evergreen, coriaceous, margin entire or sparsely serrate and inflorescence leafless at base, from the genus Pygeum, which was referred by Kalkman to a section of Prunus subgen. Laurocerasus in having flowers with a biseri-ate, usaally regularly 5-merous perianth, petals in shape and demensions distinct from sepals, 2 or more times as long as the latter, leaves sparsely serrate or rarely entire, while in the genus Pygeum the perianth segments 5-10 (-15) and in most of its species petals not or hardly differt from sepals, or, if sometimes petals and sepals distinguishable in shape, but petalsat most 1½ (very rarely up to 2) times as long as the latter. leaves always entire. The 13 species and 9 forms of Laurocerasus recognized inChina, among them 4 new species and 5 new forms have been discri-bed, are divided into two groups which are regarded inthis treat-ment as sections, i. e. Sect. Phaeostictae Yü et Lu and Sect. Laurocerasus. The Sect. Phaeostictae Yü et Lu, containing 2 speciesand 5 forms, is characterized by leaves with densely dark glan-dular points beneath, while Sect. Laurocerasus, comprising 11 species and 4 forms, is grouped into 4 series which distingtuish from Sect. Phaeostictae by leaves epunctate on lower surface. In respect to the geographical distribution the genus Laurocerasus occurs mainly in tropical regions, i. e. from Africa, southern Asia, southeastern Asia, New Guinea to South America, some species spread to subtropical and cooltemperate areas, i. e. from southwestern and southeastern Europe to Near East, China and Japan. There are about 20 species distributed in the Old world, of which 13 species have been recorded in southern China and other regions (Vietnam, Upper Burma to northeastern India) which are adjacent to it, amount to 65% of the total number of the Old world. It has shown clearly that the distribution centre of Laurocerasus lies in southern China and its neighbouring regions. There are only few species extending their areas outside this distributional centre. In China the genus is restricted in southern parts of southern slopes of the mountain Qin Ling, the southwestern part of Shanxi and southeastern part of Gansu are the northern dist-ributional limits of this genus. By analysis of the distribution of species in China the great majority of them inhabit the southern parts of Yangtze River where exist the greatest number of species of Laurocerasus, particularly abundant in southern and southwestern parts of China. There are 13 species occupied in China, of which the species distributed in southern (8) and southwestern China (7) amount to 61. 5% and 54% of the total number of the whole China respeetively. From the above faets we may now concluded that the greatest density of species in the distributional centre of Laurocerasus is now found in southern and southwestern Parts of Cilina.
