148 



DEVELOPMENT OF OKGANIC LIFE 



[Ch. IX. 



characterised by distinct species of animals and plants * 

 The dates of the successive appearance of certain classes 

 orders, and genera, those of higher organisation always 

 characterising rocks newer in the series, have often been mis- 

 stated, f and the detection of chronological errors has engen- 

 dered doubts as to the soundness of the theory of progression. 

 In these doubts I myself indulged freely in former editions 



But after numerous corrections have been 

 made as to the date of the earliest signs of life on the globe 



of this work. 



more 



animal or vegetable, first entered on the stage, the original 

 theory may be defended in a form but slightly modified. 



Fossil plants. — To speak first of the vegetable creation 

 recent investigations have made it more and more clear that 

 the oldest known flora was characterised by a great predomi- 

 nance of cryptogamous plants. In the Devonian flora of 

 North America the lycopodiaceous genera, such as the Lepi- 

 dodendra, were the most numerous, while the associated 

 plants, such as Sigillarise, ferns, and Coniferae, although they 

 are specifically distinct, agree generically with those of the 



_ next in succession. It had 



been suggested that the absence, in the true coal, of the 

 higher grade of flowering plants, (the dicotyledonous angio- 

 sperms of Brongniart,) which now constitute four-fifths of the 

 vegetation of the globe, might be explained by supposing that 

 the fossil species represent those only which grew in a par- 



come 



swamps 



mor 



become 



& 



mountainous res 



But, although it 



ersally admitted 



of the coal grew on the spots where we now find that fuel, 

 yet there are many vegetable remains in the associated sand- 



which must have been drifted from a distance or 



stones, 



* In my work on the Antiquity of 

 Man, 1863, I have given, p. 295, a 

 concise statement of the doctrine of 

 progression as laid down by Prof. 

 Sedgwick, the late Hugh Miller, M. 

 Agassiz, Prof. Owen, and Profs. Bronn 



and Adolphe Brongniart, as applied both 

 to the animal and vegetable worlds, 

 which I need not repeat in the present 



CililDtCI 1 



t See my Elements of Geology, P- 

 853. 









8' 



