REVISION OF EXTRA-TROPICAL SOUTH AFRICAN ASCLEPIADACE^E. 313 



Aschpias L., Cynanchuvi L., Dir.mia R. Br., Pentarvhinum E. Mey., 

 and several Cempiujinm, as Orthanthera Wight, Dccaerras Harv. 

 and Dich(Bli(i Harv. Not much is known as yet about the Kalahari 

 region, very few plants having heen brought from there. The coast- 

 belt between the mouth of Orange River and Walfish Bay is ahiiost 

 unexplored, especially south of Angra Pequena, Prof. Schinz and 

 Dr. Marloth in the western, and myself in the eastern Kalahari 

 having collected no Asclepiads in this region within our boundary. 



Before proceeding to the south-eastern region, I may be allowed 

 to make a few remarks concerning the eastern limits of the Kalahari 

 region. When Mr. Bolus Avrote his valuable Sketch of the l^lora of 

 South Africa, nothing was known about these parts, and hence the 

 author preferred to adopt Grisebach's boundaries. Since then, 

 however, extensive collections were made in the Transvaal and 

 the Orange Free State, through both of which countries I went 

 myself, collecting extensively in the former, but little only in the 

 latter, yet sufficient to give me an idea of the distribution of the 

 main types. From my own observations and from those of others, 

 I think that the Kalahari should be limited in the south- east by 

 the southern boundary of the Orange Free State, and comprise only 

 the south-western half of this country ; from the neighbourhood of 

 Potchefstroom the line should then go north to the head-waters of 

 the Limpopo or Crocodile River, and from there north-east to the 

 western extremity of the Zoutpansbergen. All the country lying to 

 the east of this line should be included in the south-eastern region, 

 with which it has much more affinity in its flora than with the 

 Kalahari. 



The south-eastern region as defined above is, as far as Asclepi- 

 adaccoi are concerned, probably the richest country in the world. 

 Of the fifty-four South African genera of Asclepiadacea, we find 

 forty in this region. Some of these extend north to the tropical 

 Africa, others are typical to the region, such as Chloroci/athus Oliv., 

 lihomhonema Schltr., Fanninia Harv., PeHrjlossum Dene., Krebsia 

 Harv., Lusiostelma Bth., Macropctalum Burch., Sisijranthus E. Mey., 

 Riocreuxia Dene., and Anisotoma Fenzl. With the single exception 

 of Ectadinm vut/atum E. Mey., all the species of the suborder Peri- 

 plocoidem have their home here. 



As in the other features of the flora, there is a decided affinity 

 to the tropical African species, especially to those in Angola. 

 Little or no affinity we find to Madagascar in the presence of 

 Pentopir,tia natalensis Schltr., a species being, however, so well 

 distinguished from the Madagascarian ones that it may be regarded 

 as a type of a well-marked subgenus, LeptupcBtia, a name already 

 proposed by Harvey. The want of marked affinity to the high 

 mountains of tropical Africa, especially the Kilimanjaro, the 

 Kenia, the Ruwenzori, and the highlands of Abyssinia, is best 

 explained by the circumstance that Asclepiadaceie are not fond of 

 the windy and cloudy mountain-heights. Even here in the south- 

 eastern region, where they are so numerous, their number is but 

 very small on the high mountains. 



By far the largest genera in the south-eastern region are Schizo- 



JouRNAii OF Botany. — Vol. 34. [July, 1896.] y 



