56 BUREAU OF AMERICAN ETHNOLOGY [bull. 54 



would be expected to occur in a region which was slowly drying up, 

 and present conditions are just such as one would be led to expect. 

 Hence it seems very probable from the archeologic evidence that there 

 has been progressive desiccation. 



Botanical Evidence of Change of Climate 



It would naturally be expected further that a change of climate 

 would leave some impression on the native vegetation by which it 

 could be detected. Climatic changes are necessarily gradual, and 

 much of the vegetation could slowly adapt itself to the progressive 

 changes by change in characters and habits to enable it to meet the 

 altered conditions; but if the change is still in progress or has very 

 recently ended it would be apt to manifest itself in the relations of 

 plant formations to one another and in "relicts" or stragglers left 

 over in the most favorable habitats. 



While it is true that during 3,000 years some species may be altered 

 to a slight extent, others may be introduced by various means, and 

 others may come into existence suddenly (mutation), and that the 

 relations of formations and associations of plants may have changed 

 in some measure, yet it is highly improbable that there has been a 

 marked and widespread modification of the flora within that time. 

 However, the relation of the two principal plant formations of the 

 region seems to afford some evidence of progressive climatic change. 

 This may be seen in the stress zone between the pinon pme-cedar 

 formation and the rock-pine formation. Pinon pines and cedars 

 grow in drier situations than do rock pines. In the area under dis- 

 cussion rock pine occurs on the higher parts of the mesas, back 

 toward the mountains, while pinon pine and cedar are confined to the 

 lower portions, down toward the rim of the Rio Grande canyon. 

 At a distance of one to three miles back from the Rio Grande the two 

 formations meet and here there is a battle for occupancy of space. 

 If in this struggle between these two plant formations the pinon pine- 

 cedar formation is the successful competitor and gradually encroaches 

 on the rock-pine formation, and if such encroachment is widespread, 

 this condition probably indicates progressive desiccation of the 

 country. That is the condition in this region. If the rock-pine 

 formation were extending into the territory of the formation below 

 it, there would be rock-pine seedlings as outposts of the invasion, and 

 their presence would be evidence that conditions in the new territory 

 were favorable for their growth. From the lower extension of the 

 formation rock-pine seedlings are almost entirely absent. The outer- 

 most individuals are large trees, in many cases the largest of the 

 formation, possibly several centuries old, indicating that in the early 

 stages of their growth conditions were more favorable for the species 

 to obtain a start and that no such favorable period has occurred since. 



