660 STUDIES IN FOSSIL BOTANY 



Angiosperms, hitherto the most obscure subject in the 

 phyldgeny of plants, is to be sought among the great 

 plexus of Cycadophytes, which overspread the world 

 during the Mesozoic Period. 1 



This conclusion opens up the question of the rela- 

 tion of Monocotyledons to Dicotyledons. If the 

 Angiosperms were derived from Cycadophyta, it would 

 appear to follow that the Dicotyledons were first 

 evolved, for their structure has clearly much more in 

 common with the Cycad type than that of the Mono- 

 cotyledons. The latter would thus be regarded as a 

 branch line of descent, diverging, no doubt at a very 

 early stage, from the main Dicotyledonous stock. This 

 view has been maintained, on other grounds, by various 

 modern botanists. So far, however, as the palaeonto- 

 logical record shows, the two classes are of almost 

 equal antiquity, both appearing for the first time in 

 Lower Cretaceous rocks. By the Upper Cretaceous 

 age the Angiosperms had already seized the dominant 

 position which they now hold ; the Monocotyledons 

 were always subordinate in numbers to the other class, 

 but the occurrence of typical Palm-wood in Cretaceous 

 rocks is a striking proof of the early evolution of 

 one of the most characteristic Monocotyledonous 

 families. 



The relation of the Bennettiteae to the Pterido- 

 sperms, and through them to some early race of Ferns, 

 has been sufficiently emphasised in preceding pages. 

 We are thus led to the conclusion that the whole of 

 the dominant sub-kingdom of Flowering Plants, if akin, 



1 See Arber and Parkin, " The Origin of Angiosperms, " Journal Linn. 

 Soc. (Bot.), vol. xxxviii. 1907. 



