90 THE STORY OF PLANT LIFE 



Club Moss types, Fern types, and some of the still 

 higher Gymnospermous extinct plants, Cordaitales, 

 and some Pteridosperms, and Sphenophylls, all the 

 three last being extinct types. 



To seek for the origin of these types is at present 

 impossible. In the Cambrian and Silurian rocks only 

 anomalous types, possibly Algae or possibly Lycopod 

 types, occur. But the evidence favours the view that 

 the Devonian types were derived from some earlier 

 types whose remains have not been preserved. They 

 are less specialised, or more primitive than the later 

 Carboniferous types of the same groups. 



In the Coal-measures the flora is far more luxuriant 

 and rich in species than the Devonian. Moreover, 

 a new type or habit is introduced in the plants with 

 seed-like fructifications, or the Pteridosperms, and 

 Lycopods with the same characteristics. Special 

 adaptations to the humid conditions were introduced 

 in the secondary wood of the arborescent types of 

 Horsetails and Club Mosses. The Cycad-like character 

 of some of the so-called ferns, and some other plants 

 also introduces us to a higher type. Coniferous types 

 occur at the close of this period, and in the Permian 

 in which the flora is more or less the same. The 

 Ginkgo-like type is foreshadowed in part in the Cord- 

 aitales which also combine coniferous characters. 

 We thus have in the Coal-measures the synthetic 

 types from which in later epochs, Cycads, Conifers, 

 and Ginkgo have been evolved. Moreover, the seed 

 habit is also in the Coal-measures developed as the 



