FLO BA OF ADEN. 
63 
7, Geographical Relations of the Flora of Aden, 
With regard to the geographical distribution of the Aden plants we 
may distinguish six groups : 
1. To the first belong the species which are endemic in Aden, 
Anderson considered 14 out of his 94 plants to be endemic, viz. : — 
Cleome. paradoxa It. Br. 
Cltome joruinosa T. Anders. 
Mama Thomsoni T. Anders. 
Spharocoma HooJceri T. Anders. 
Hibiscus Welshii T. Anders. 
Bterculia arabica T. Anders. 
Taverniera glauca Edgew, 
Acacia Edgeworthii T. Anders. 
Ttychotis arabica T. Anders. 
Convolvulus sericophyllus T. Anders. 
Anarrhinum pedicellatum T. Anders. 
Campylanthus junceus Edgew. 
Lavandula setifera T. Anders. 
Euphorbia systyla Edgew. 
Later botanical explorations, especially in S. Arabia, Eritrea, 
Somaliland, and Socotra, have shown that only 3 of the 14 are endemic 
in Aden,fy^., Cleome pruinosa , Marua Thomsoni , and Hibiscus Welshii . 
In addition to these, the following species seem to be confined to 
Aden : — 
Toly gala Thurmanniana Chod. Heliotropium adenense Guerke. 
Fagonia glabra Krause Echiochilon longiflorum Benth. 
Crotalaria Schweinfurthii Defl. Albuca Yerburyi Ridley. 
Pulicaria adenemis Schweinf. And the variety GypiopUla montan 
var. diffusa Balf. 
There are, therefore, 10 species endemic in Aden, forming just JL 0 f 
the total number. It is more than probable, however, that further 
explorations of the neighbouring countries will reduce even this limited 
number of endemic plants. 
3. The plants of the second group belong geographically to two 
narrow strips of land along the Red Sea, beginning at about 23 N. Lat., 
he one on the African side passing over into the coast region of Somali- 
land, whilst the other comprises Tehama and goes as far as the boun- 
ty 16 * of Yemen and Hadramaut. To. the same region belong all the 
islands of the Red Sea south of the Tropic of Cancer. 
Aden has the following species in common with this area : 
Argyrolobmm arabicim, Tephrosia pogonostigma, Aeaeia hamulosa, 
Corattocarpus erostris, Statice axillaris , Statioe cylindrifolia, Heiiotrop- 
tum pterocarpum (also in Socotra) Unarm macilenta (also in the Sinai 
Peninsula) Anticharis arabica, Halopeplis perfoliata, Salsola lorskalii, 
Anabasis tlrenhergii, Euphorbia Botta, Euphorbia cuneata, Sphasrocoma 
Hooken . 
