ORIGINATION OF SELF-GENERATING MATTER 



291 



slender central cylinder and a thick inclosing cylinder of thin- 

 walled tissue have been alluded to in this connection, but these great 



Fig. 4. — Aspect of the vegetation in regions with no well-marked rainy seasons of 

 regular recurrence. (Below) The bolson of Las Vegas, Nevada. (Above) Bajadas of 

 minor range of mountains near the shore of the Gulf of California, San Felipe Bay. 

 The plants comprise spinose forms with very reduced shoots and leaves, which have 

 not developed storage capacity. 



sporophytes probably stood in swamps, or at least were hygrophytic 

 in habit, and by the requireTients of their separated gametophytic 



