SEED-BEARING PLANTS 
411 
364. Distribution. The cycads and their relatives are 
all tropical or subtropical. Four genera (Microcycas, 
Zamia, Ceraiozamia, Dioon) occur in the western hemi- 
sphere, with the chief center of distribution in Mexico; 
and five genera (Cycas, Bowenia, Macrozamia, Encephal- 
artos, and Stangeria) in the eastern hemisphere, with 
FIG. 3030. Wilhelm Hofmeister (1824-1877). His comparative studies 
of the history of development of mosses, vascular cryptogams, and seed- 
bearing plants, disclosed the fact of an alternation of generations through- 
out those forms, and afforded the basis for a correct interpretation of the 
genetic relationship of the great groups of plants. 
the chief center of distribution for the first three in Queens- 
land, Australia. Encephalartos and Stangeria are confined 
to Africa. 
