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THE MUSSiENDAS OF THE AFRICAN CONTINENT. 



By H. F. Wernham, B.Sc, 

 Department of Botany, British Museum. 



The Rubiaceous genus Musscenda occurs in the warmer parts 

 of Asia and Africa, and in the Mascarine and Pacific Islands. It 

 is notable for its showy flowers, with the frequent development in 

 many species of one or more of the calyx-lobes, in the exterior 

 flowers of the corymbose inflorescence, as an attractive petaloid 

 lamina. This phenomenon is parallel, biologically, with the 

 development of "ray" flowers in Umbelliferce, Composites, &c, in 

 which, however, the lobes of the corolla, not of the calyx, are 

 concerned. Its significance lies in the attraction of insect- visitors 

 to an entire, compact inflorescence, instead of to a single flower, 

 so that several flowers may be cross-pollinated at a single brief 

 visit from a suitable insect. The floral arrangement is correlated 

 with that " umbellifloral tendency " which lies at the root of the 

 Rubiaceous ancestry * — i. e. the presentation of a continuous 

 floral surface to visiting insects. 



Musscenda is particularly interesting from the aspect of the 

 biological principle of insect-attraction. The tube of the corolla 

 is typically long and slender in all the species and does not vary 

 much; but the limb displays considerable variation in relative 

 size, in accordance, usually, with the species. In some species 

 (§ Landia) — most of those native in Madagascar, for example, 

 about a dozen in all — the calyx-lobes are all normally small and 

 equal, or nearly so. In these the attractive function is adequately 

 discharged by the corolla, for the limb is amply developed. The 

 same applies to the African M. elegans, dealt with in the present 

 paper, in which the bright scarlet corolla-limb may attain 6 cm. 

 in diameter, while in none of the specimens are the calyx-segments 

 modified into an attractive petaloid lamina. In species like* 

 M. tenuiflora, on the other hand, the width of the inconspicuous 

 corolla-limb is reduced to a few millimetres, and the calyx- 

 segments lying towards the periphery of the inflorescence are 

 petaloid. M. [arcuata seems to represent a transitional stage in 

 this regard ; "the petaloid development is quite rare, and the 

 corolla-limb is of very variable relative width. 



The examination of several recent collections in the National 

 Herbarium has directed my attention particularly to the African 

 species of the genus, and has revealed the existence of several 

 novelties. These are described below, together with references to 

 the descriptions of all the known species indigenous in the African 

 continent. Details of the specimens in the two principal British 

 herbaria are given, as well as a key to all the species, with one or 

 two doubtful exceptions. 



My grateful acknowledgments are due to the authorities of 

 the Kew Herbarium for placing the material under their control 

 freely at my disposal. 



* See Wernham, New Phytologist, xi. (1912), 226, 227. 



Journal of Botany. — Vol. 51. [August, 1913.] t 



