14 PLANT GEOGRAPHY 



different from the present; and that life itself was 

 represented by successive groups of organisms also very 

 different, at least in their numerical proportions, from 

 those of to-day. Not only is there no a priori reason 

 against the South Pole being also a centre of origin and 

 dispersal; but it is, perhaps, more probable that life 

 should have originated in the hot, moist climate of 

 equatorial regions where it is seen to-day in its most 

 prolific luxuriance than in the more frigid neighbourhood 

 of either pole. We know nothing, however, as to the 

 relation in time between the primitive cooling of the 

 globe and this first appearance of life upon it. 



CHAPTER IV 



FLORAS OF THE PAST 



FRAGMENTARY as is the evidence, it is now apparent 

 that the story of the evolution of plant-life is continuous. 

 We cannot, it is true, trace among fossil plants a passage 

 from Algae to Bryophyta, or from Bryophyta to Pteri- 

 dophyta. We have, in fact, little, if any, evidence of 

 the existence of mosses in Palaeozoic times. They 

 might be supposed to have contributed an important 

 element in the vegetation of the warm, moist land- 

 surfaces of Carboniferous times ; but, in spite of the fine 

 state of preservation of many equally delicate plant 

 structures from that age, they are hardly represented. 

 Among Vascular plants, however, there is a distinct 

 and continuous succession from Devonian times to the 

 present day. 



Although in the Devonian rocks all the main existing 

 divisions of the Pteridophyta, viz. Horsetails, Ferns, 

 and Club-mosses, and a primitive group of Gymnosperms 

 (Cordattes) have already made their appearance on the 

 earth, there is evidence of the existence in that age of 

 generalised types, combining the characters of several 



froups and thus suggesting their ancestral character, 

 n later series of rocks other groups of Gymnosperms 

 appear, followed in Cretaceous times by Angiosperms. 

 Nor are the undoubted facts of degeneration within 

 these various groups in the least a contradiction of 



