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as one of the most isolated. It is allied to Sphaerophysa 

 which likewise belongs to the interior of Asia, and to Colutea 

 which is distributed from the south of Europe to the western 

 Himalaya. 



Holopleura, so far as I can learn, is insufficiently known 

 and there may be some doubt as regards its right to generic 

 rank. REGEL says that it is related to Carum and Rumia. 

 Miltianthus is related to Zygophyllum. 



Among the endemic species scarcely any one stands 

 isolated. Whichever one be named, it is possible to indicate 

 closely related species in the surrounding countries, more 

 especially those towards the South and South-west. Through 

 more intensive systematic studies one could probably enumerate 

 a series of pairs of vicarious species. Studies of this kind 

 have not been undertaken here, as I have restricted myself 

 to the investigation of the distribution of the genera which 

 contain endemic species in the lowlands of Transcaspia. The 

 following genera have their main distribution in the Medi- 

 terranean countries, especially in the eastern ones, and in 

 Nearer Asia whence some of them extend right into Central 

 Asia. 



Heliotropium Pterotheca Allium 



Lappula Scorzonera Limodorum 



Rochelia Convolvulus Cistanche 



Gypsophila Isatis Hypecoum 



Herniaria Malcolmia Trigonella 



Saponaria Peltaria Crucianella 



Silene Sisymbrium Haplophyllum 



Centaurea Crypsis Scrophularia 



Echinops Lepturus Tamarix 



Jurinea Lagochilus Cachrys 



Rhaponticum Phlomis Ferula 



Matricaria Tulipa Valerianella 



The following genera seem to have their main distri- 

 bution more to the East, in the interior of Nearer Asia and 

 in Central Asia: 



