xliv BOTANY OF SOCOTRA. 



is responsible for other five. Most of the species, thirteen, are cosmopolitan 

 tropical plants, and seven are widely spread in the tropics of the old world. 

 One species, Ci/perus proteinolepis, is primarily an Arabian species, but a 

 variety of it, which also occurs on Socotra, extends to upper Egypt ; and there 

 is an endemic variety of Cyperus conglomeratus, a species with a geographical 

 area extending from north-east Africa through Arabia to Beloochistan and 

 Afghanistan. 



In Convolvulacese, forming more than three per cent, of the flora, there are 

 seven endemic species, and of these the most interesting are the plants I have 

 described as species of Breweria. Neither B. fastigiata nor B. glomerata adjust 

 themselves to the generic character, but appear, especially the former, to share 

 the features of more than one allied genus ; and a like remark applies to 

 Porana obtusa, which I have included in what is a very polymorphous and at 

 present unsatisfactorily-defined genus. 



Rubiacese, Asclepiadese, and Boraginese constitute each one-thirty-first part 

 of the flora, and are deserving of special mention. 



Rubiacese is only about half as extensively represented as Composite?, which 

 is noteworthy on account of the inverse relation prevailing in tropical Africa 

 and the Mascarene Islands. More than half of the species are endemic, and 

 there is one endemic genus. The most remarkable feature in the family is 

 the great development of the genus Dirichletia, hitherto known in four species 

 from tropical Africa, Madagascar, and Somali-land. The Somali-land plant 

 occurs on Socotra and also three endemic species— one, D. obovata, being quite 

 one of the commonest trees upon the shore-plains and hill-slopes. As might 

 have been expected, the Socotran plants necessitate considerable emendation 

 in the described generic character. Placopoda, the endemic genus, is a near 

 alley of Dirichletia. Of other plants in the order, the endemic Musscenda 

 capsulifera may be noticed on account of its capsular dehiscing fruit, in which 

 feature it resembles the Nile-land M. luteola, already recorded as an aberrant 

 form in the genus. 



Asclepiadeae is another order with a remarkable development in Socotra. 

 Our material does not allow of specific determination of five distinct plants 

 belonging to the order, and the species of another is doubtful; but of the 

 twelve we have named eight are endemic, and two of them form monotypic 

 endemic genera. The endemic genera Mitolejns and Cochlanthus belong to 

 Periplocece, and have affinity with African genera. I have only described two 

 endemic genera from the island, but it is not without violence to generic 

 characters, as defined by Hooker and Bentham, that other species are placed 

 in the genera to which they are assigned. Thus Secamone socotrana diverges 

 from its generic type in the internal villous appendages to the corolla, and, like 

 the Mascarene and Madagascar members of the genus, has sinistrorse aestivation 



