APOGAMOUS FERNS. EVOLUTION OF THE SEPARATE SPECIES 

 the approximate distribution of the species in Europe as compiled in a recent study by 

 Nordhagen (1947). 



«^- 





, a b 



Fig. 196. Meiosis in Dryopteris Borreri var. polydactyla Dadds in balsam after acetocarmine. x 1000. 

 a. From an eight-celled sporangium with regular pairing, b. From a sixteen-celled sporangium 

 with virtually no pairing. 



Fig. 197. Map of the northern limits oi Dryopteris Borreri Newm. in Europe. 



After Nordhagen (1947). 



With regard to chromosome numbers in D. Borreri it has already been shown in 

 Chapter 4 that a polyploid series is present in grades ranging from diploid to pentaploid, 

 though not all of the same constitution. We are still imperfectly informed about the 



188 



