362 GYMNOSPERMS 



The archcgonium and cmbryogcny keep Ephedra definitely in the 

 gymnosperms; while other features keep the other two genera with 

 Ephedra. Otherwise, only the naked ovule would keep Welvntschia 

 and, especially Gnelum, out of the angiosperms. 



The three genera are so different in appearance and in the details 

 of life-histories that no one could have given rise to either of the 

 others. Their connection with any of the rest of the living gymno- 

 sperms is just as doubtful as any relationship with the angiosperms. 

 They are gymnosperms because they are seed plants with naked 

 ovules, and Ephedra, carrying the other two genera with it, has a 

 gymnosperm life-history. Otherwise the whole assemblage would 

 be an isolated group, without even a problematical relationship. 



It seems best to treat the three genera separately, and, on the 

 basis of the evolution of the female gametophyte, the order of treat- 

 ment should be Ephedra, Welwitschia, and Gnetum. 



EPHEDRA 



Ephedra is a low, profusely branching shrub (fig. 344). In the 

 region shown in the illustration, near Palm Springs Canyon, Cali- 

 fornia, it is very abundant and often serves as a sand binder. Some 

 North African species trail over other plants and climb somewhat. 



Geographic distrihution. — It is a xerophytic genus, at its best 

 in mountainous or rocky places, or in sandy, desert regions, like that 

 shown in the illustration. 



Markgraf,-^"' in Die natiirlichen Pjlanzenjamilien, estimates the 

 number of species at 35. Pearson^^'' lists 32, not including the well- 

 marked Ephedra compacta, found near Tehuacan, Mexico. 



The species are somewhat equally divided between the Western 

 and Eastern hemispheres. Pearson assigns 17 species to the Old 

 World and 14 to the New, with 6 to North America (there should be 

 7 with E. compacta), and 8 to South America. 



In North America they are most abundant in New Mexico, 

 Arizona, and California, although they are found in the states border- 

 ing these on the north. Only one species. Ephedra anlisyphilitica, 

 gets as far east as Texas. There are some in northern Mexico, but 

 none have been reported between northern Mexico and the small 

 Ephedra compacta, near Tehuacan. In South America they are most 



