i9i 2] WATSON— PLANT GEOGRAPHY OF NEW MEXICO 217 



d) Plants as Erodium or Draba bloom much earlier in the cooler 

 but moister mountains than on the warm but arid plain. 



e) A patch of mesophytic spruces (" Canadian zone") is very 

 frequently entirely surrounded by the more xerophytic oaks of the 

 " Transition zone." 



/) The tendency of the higher zones to creep down the canons 

 and of the lower zones to creep up the ridges receives a much more 

 plausible explanation in connection with the supply of moisture 

 in the two situations, than through the cooling effects of descend- 

 ing currents and the warming effects of ascending ones. 



5. An arrangement of "zones" should be based on all factors 

 determining the distribution of life and not on one only, especially 

 in a region where that one is of secondary importance. 



6. Most of the plants of the mesa do not show the marked 

 seasonal periodicity of the east. 



7. Plants having large organs for the storage of moisture do 

 show seasonal periodicity. 



8. A characteristic of much of the vegetation is the ability to 

 lie dormant until the rains come, and then to make an exceedingly 

 rapid growth and reproduction. 



9. The differences in amount and distribution of rainfall in 

 different years causes a more marked response in plants (shown by 

 height and reproductive activities) than in more humid regions. 



10. The region is a particularly good one in which to study 

 physiographic plant ecology' because of the abrupt differences in 

 physiography and climate. 



University of New Mexico 



Albuquerque 



