MONOGRAPH OF THE BBITISH SPECIES OF EUPHRASIA. 



335 



species do intersect or occupy portions of the same area.* From 

 this we may conclude that the species of each series had each a 

 common ancestor, tlie first of which the Professor names E. tri- 

 cuspidata s. 1., the second E. Salisbiuyensis s. 1., and he thinks that 

 the ancestor of tlie first series was older than that of the second, 

 and that the latter was descended from the former, and for the 

 following reasons : — The distribution of E. tricuspiilata s. 1. is such 

 as would betoken its existence in the tertiary epoch ; it has a con- 

 siderable east and west extension in South Europe, and is found in 

 the mountains of the South Europe peninsulas ; it is morpho- 

 logically nearer to the Japanese species than is E. Scilisbun/ensis ; 

 it exhibits in its descendants a greater variety of forms or species, 

 thus betokening a greater lapse of time for their development ; 

 lastly, the flowers of E. tricuspiilata s. 1. are larger and are fitted 

 for zenogamy, while the flowers of the second series are autogamic. 



Scheme V. 



Parent Species. 



Eecent Species. 



E.PalcBO-tncujpidO'Ui^' EJaponica,s.h. E.msigniss.l. 



•E.alpina, 



\ » 



Eiialisburgensis.s. I. 



E. tnciispidctior s. I. 



To repeat — E. tricuspidata s. 1. at the end of the tertiary epoch bad 

 its extension in the mountains of Mid and South Europe ; this type 

 also extended to East Asia. The glacial epoch then broke up the 

 connection and diminisbed its extension in the northern portion of 

 its area, and at the same time brought about the development of 

 E. Salisbuninisis s. 1. fitted to resist the severity of the climate. At 

 the end of the last glacial epoch, under more favourable conditions 

 E. tricuspidata spread from the plains of South Europe back into 

 the valleys of the neighbouring mountains, also into the Apennines 



See Prof. Wettstein in Oexterr. Botan. Zeitschrift, 1893. 



