No. 539] ORIGIN OF SPECIES IN NATURE 647 



number of observations is identical. But the greater 

 familiarity with the territory and the fact that hIhtvu. 

 tion may be continued throughout the seasons offers cer- 

 tain advantages. It is a question which must be decided 

 for individual cases by every investigator along this line. 



since its answer must depend on local conditions, such as 

 proximity to residence, climate, whether arid or temper- 

 ate, etc. A garden, for instance, offers as good if not 

 better opportunities to observe the appearance of new 

 forms as does the field. Here all the requirements for 

 such work are met with, i. e., large numbers grown under 

 highly favorable conditions. Parks, nurseries and espe- 

 cially the larger botanical gardens, where are kept accu- 



