228 



morphology 



(7) Gnetales 



General character. — This group comprises three very distinct genera: 

 Ephedra, with about fifty species distributed throughout the arid regions 

 of the Mediterranean basin and adjacent Asia, and also in the arid regions 



Figs. 511-516. — Ephedra: 51T, branches bearing ovulate strobili; 512, branches 

 bearing staminate strobili; 513, staminate strobilus, showing staminate "flowers" in 

 axils of bracts; 514, ovulate strobilus; 515, an ovulate "flower"; 516, decussating 

 bracts of the ovulate strobilus. — After Watson. 



of western North America and* South America; Tumboa (often called 

 Welwitschia), represented by a single species in the arid districts of 

 western South Africa ; and Gnelum, with about fifteen species distrib- 



