Northern Mexico: Yucca Vegetation. 299 
great Basin and still others southern California and the great plain regions of 
Texas, Colorado and Nebraska. The capsular Yuccas are more primitive than 
the baccate species, which may be looked upon as derivatives, while the spongy 
fruit of Cleistoyucca is a desert tumble fruit. 
IR AT; 
Fi En ala. 
8: 10. Peireskia guatemalensis Rose in a desert near El Rancho above Zacapa, Guatem 
Photograph by O. F. Cook. 
