E. V. Wulff 



— 90 — Historical Plant Geography 



noted long ago. According to Engler, such discontinuous areas of 

 genera found only in South America, Africa, and Madagascar may be 

 divided into three main groups. To the first he refers genera having 

 numerous species distributed in South America, of which only a few are 

 found also in Africa, and monotypic genera distributed both in South 

 America and Africa, related genera of which are found in South 

 America. For instance, Telanthera {Amaranthaceae) has 45 species in 

 South America, of which only one is found in western Africa; Paullinia 

 (Sapindaceae) has 80 species in South America, only one of which 

 grows in Africa. 



To the second group are referred genera having maximum distri- 

 bution in South America, but a few species not found in South America 

 grow in Africa. For example, Copaifera (Leguminosae) has 10 spe- 

 cies in South America and 2 in Africa, of which one is related to 



Fig. 18. — Australian discontinuous area of the section Erythrorhiza of the genus Drosera. 

 (After DiELs). 



a species found in Cuba; Asclepias {Asclepiadaceae) has 58 species in 

 South America and 2 in Africa. Here we may refer also the very in- 

 teresting area of the genus Ravenala, distributed on Madagascar and 

 in South America. 



To the third group are referred genera having several species in 

 South America and several in Africa or represented in their floras by 

 a single species each. For instance Sphaeralcea {Malvaceae) has 21 

 species in South America and 4 in Africa (Cape Province); Amanoa 

 {Euphorhiaceae) — 2 species in South America and also 2 in western 

 Africa; Chlorophora (Moraceae) — i species in tropical America and i in 

 Africa. 



