DISTRIBUTION AND RELATIONSHIPS OF THE CYCADEOIDS 
and it is conceivable that all the antecedent types of the angiosperms are 
equally discrete, always separate lines, leading back to the first forests that 
clothed the land in the Devonian. And throughout all later time it may 
well be believed that with the poles where they now are, and with that 
tremendous rhythmic diastrophism or emergence and subsidence of the 
continents, there was an ever-present plasticity in the plants of the arctic 
areas. But along with the theory of hardiness and invasive power for the 
plants of the high north and far south would perforce go a similar poten- 
tiality in plateau and mountain vegetation. 
EXPLANATION OF PLATE VII 
Above: Apical view of Cycadeoidea dacotensis (type) showing terminal helicoid of 
young chaff, enveloped fronds, and scale leaves, with various fruit buds, about 3^ natural 
size. 
Below: Cycas revoluta (left), showing cone about 1,5 inches high, and (right) the same 
in a younger stage of growth. 
These figures illustrate extreme cycadophytan types. 
