E. V. Wulff — xiv— Historical Plant Geography 



Chapter 6 



PARALLELISM IN THE GEOGRAPHICAL DISTRIBUTION OF 

 PLANTS AND ANIMALS AND CORRELATION BETWEEN 

 THE DISTRIBUTION OF PARASITES AND THAT OF 

 THEIR PLANT HOSTS: — Parallelism in the distribu- 

 tion OF PLANTS AND ANIMALS — RuST FUNGI AS AN INDEX OF 

 THE DISTRIBUTION OF THEIR PLANT HOSTS — PlANT-LICE AS AN 

 INDEX OF THE DISTRIBUTION OF THEIR HOSTS 94 



Chapter y 



ARTIFICIAL FACTORS IN THE GEOGRAPHICAL DISTRI- 

 BUTION OF PLANTS: — Loss by cultivated plants 



(and BY weeds infesting THEM) of their ABILITY TO 

 maintain an independent existence AND TO SPREAD INDE- 

 PENDENTLY — Geographical limits to the distribution of 

 EXOTICS — Conclusions 102 



Chapter 8 



NATURAL FACTORS IN THE GEOGRAPHICAL DISTRIBU- 

 TION OF PLANTS : — Wind as a factor in the dispersal 

 OF PLANTS — Water as a factor in the dispersal of 

 plants — Animals as a factor in the dispersal of plants 



— Significance of natural factors in the distribution of 

 plants — Barriers to dispersal: their influence on 



PLANT distribution — STOCKING OF UNOCCUPIED TERRITORIES 



— Conclusions 115 



Chapter g 



THE MIGRATIONS OF SPECIES AND FLORAS AND THEIR 



CAUSES : — Migration theory — Periodicity in the 

 growth and development of plants — Disharmony be- 

 tween THE biological PECULIARITIES OF SOME SPECIES AND 

 THEIR PRESENT-DAY HABITAT CONDITIONS — SpECIES NOT 

 HAVING A FULL CYCLE OF DEVELOPMENT — EXTINCTION OF 



SPECIES — Climatic changes in the Tertiary period and 



THE RESULTANT SHIFTING OF VEGETATION ZONES — ThE IcE 



Age and its effect on vegetation — Refuges of species 

 during glacial periods and migrations of species — Cli- 

 matic CHANGES AND SUCCESSIONS OF VEGETATION; THE POST- 

 GLACIAL PERIOD — Pollen-statistics METHOD 137 



