Bacterial Flora of the Semi -Desert Region of New Mexico. 225 



March 23: 



PI. a, 2 min. — 150 bacteria and 1 mold. 

 PI. b, 4 min. — 208 bacteria and o mold. 

 Average per 10 min., 685 bacteria. 

 PI. c, 2 min. — 41 bacteria and 1 mold. 

 PI. d, 4 min. — 37 bacteria and o mold. 

 Average per 10 min., 149 bacteria. 



Notk. — Plates b — 4 minutes, and d — 4 minutes, were 

 photographed to show the relative proportions between even- 

 ing and morning conditions. See Figs. Ill and IV, page 

 226. Plates were photographed March 28. 



Exp. 23 — March 17 and 18. Duplicated conditions of 

 last experiment on South Arno Street, i. e. residence district. 

 Time — 5 and 10 minutes. 



March 23: 



PI. 5 min. (7.33 p. m.) — 346 bacteria and 5 molds. 

 PI. b, 10 min. (7.33 p. m.) — 636 bacteria and 8 molds. 

 Average per 10 min., 664 bacteria. 

 PI. <f, 5 min. (7.33 A>. m.) — 103 bacteria and 7 molds. 

 PI. d, 10 min. (7.33 a. m.) — 128 bacteria and 8 molds. 

 Average per 10 min., 167 bacteria. 



It will be observed that the six experiments just recorded 

 were planned in pairs — 18 and 19, 20 and 21, etc. The object 

 was to establish a comparison of conditions between the resi- 

 dence and business portions of the city of Albuquerque. If 

 the data of Table I are borne in mind, we can also establish a 

 comparison between the country air and that of the two parts 

 of the city. 



If then we make the first comparison, that is between the 

 residence and business portions, we find that the latter uni- 

 formly shows a higher number of air bacteria, the ratios being 

 (per 10 min.) 276:1,031; 394:4,320, etc. 



Probably the second ratio of approximately 1:10 is nearer 

 the actual than the first because of the thickly seeded plates 

 in the former — some of the bacteria being prevented from 

 developing; and partly also because of the difficulties in 

 counting the colonies. 



15 



