240 



HEREDITY AND EVOLUTION IN PLANTS 



to early Palaeozoic times; the same is true of our modern 

 cycads, maidenhair tree (Ginkgo), club-mosses (Lyco- 

 podiales), and horse-tails (Equisetales). The Coniferales 

 may be traced back into the upper Carboniferous period, 

 while the most highly developed of modern plants, the 

 Angiosperms, appear to have come into existence as late 

 as about the middle of the Mesozoic era, perchance as 



TABLE V 



Ascendancy 



Periods 



Persistence and relationship of 

 great groups 



VII. Reign of Angiosperms 



Tertiary 



Cretaceous 



Comanchian 



VI. Reign of Pro-angiosperms 



Jurassic 

 Triassic 

 Permian 



V. Reign of Acrogens (High- 

 er Equisetes. Lycopods, 

 etc.) 



Pennsylvanian 

 Mississippian 



IV. Reign of Gymnospertns Devonian 



S.U. 



aJSLJS 



,-o.W. 



III. Reign of Early Land 

 Plants 



Silurian 



Ordovician 



5. Actual Fossil Land Plant rec- 

 ord begins 



4. Primofilices Early Equisetes 

 3. Basal Plant Complex with va- 

 riety of species 



II. Reign of Algae 



Cambrian 

 Precambriar. 

 (Proterozoic) 



Differentiation of Dry 



and Aquatic Plants 

 (Fossil Algse abundant) 



Land 



I. Reign -of Primitive Life 

 (Hypothetical) 



Old P r e c a m- 



brian 

 (Archeozoic) 



(Fossil Algae begin) 

 i. Primitive Protoplasm and 

 Unicellular Life 



In the above table (after Wieland), the groups are to be considered as 

 arranged on an unrolled cylinder, projected from a hemisphere; thus the 

 phyletic lines are to be pictured as converging below toward the pole, 

 and the Cordaitales as coming between the Ginkgoales and Filicales, to 

 both of which they are related. 



