INTRODUCTION 6i 



in the chain of progressive evolution. There were 

 originally only lowly types of plants of the order which 

 we now regard as the lowest in point of develop- 

 ment. These were Algae, which are found in the 

 early Palaeozoic rocks. Later there appeared vas- 

 cular Cryptogams, Ferns, Lycopods, etc., Horsetail- 

 like types, and an extinct type of Gymnosperm allied 

 to C\^cads and Ginkgo. 



In the Carboniferous, higher types of these and 

 arborescent Lycopods appeared, and many of the so- 

 called fern types had the characters of seed-plants in 

 possessing, in place of the sori of the fern, seedlike 

 fructifications. They had also some Cycad-like char- 

 acters. Some of the Clubmosses even had the same 

 seedlike habit, e. g. Lepidocarpon, 



Later Cycads, Conifers, Ginkgo, and a peculiar 

 type Bennettites appeared with primitive Angiosperm- 

 ous characters, which lead on to the ancestors of 

 the Angiosperm. 



Monocotyledons and Dicotyledons appear much 

 later in the early Cretaceous, and onward in the 

 Tertiary, but the connecting links between the Gym- 

 nosperms are not forthcoming, though theoretically 

 a type has been hypothecated which answers to the 

 Proangiosperm connecting the Bennettites type with 

 the modern Angiosperms. Thus, in this brief sketch 

 of the march of plant-life in the past, we see that 

 there were phases of life which were characterised 

 by lower and lower types, as the earlier rocks are 

 successively examined. This corresponds to the 



