1907] YOUNG— FOREST FORMATIONS OF COLORADO 343 



■ 



ing a height of only a few inches. Biologically, the under layer of 

 this formation is open, but the physical conditions of its habitat are 

 such as to exclude most plants. 



Save where artificial conditions such as fire or lumbering have 

 intervened, the continuity of this formation is comparatively unbroken, 

 except in its lower limits, where it is represented only by a few strag- 

 gling individuals. 



Observations of the physical character of the habitat of this forma- 



made 



t) 



Station 



A was on a gentle slope with a southwest exposure, at an approximate 

 altitude of 2940"^. Station B was on a comparatively level area 

 at an altitude of approximately 3150"^. A series of three obscn^a- 

 tions at these stations gave the following results: 



Temperatures 



Station A (Observations July 5, 1:45 V. M.; 27, 11:15 a. m.; September 5, 12 M,) 

 Station B (Observation July 19, 6:30 A. M.) 



_22.5cni — zi.35==> oc"* • +7.5«=» +o.p« 



Minima 5?8* 6?2 6° 11°:): ii^J 



Maxima 8° f 8° ^3 -4 14-5 X ^3* 75 1 



* Depth of 17. s«°», t Depth of 20*=°'- t Three observations. 



Relative humidity 



Station A (Observations July 5. 11:45 P. m,; 27, 11:15 A. 11.; September 5, X9 M.) 

 Station B (Observation July ip, 6:30 A. M.) 



7.5cm 



9 



dm 



Minima 34 per cent, 27 per cent. 



Maxima 6^ per cent. 59 per cent. 



Water content 



Observations 11.25*°* aa-S-ii-as*" 



Station A July 5 17.3 per cent. 



July 27 18.5 per cent. 8.7 per cent. 



September 5 21.4 per cent. 5-5 P^r cent. 



Station B July 19 16. i per cent. 11 . 7 per cent. 



The light value of the Apinus flexilis formation was taken at a 

 point where this formation overlapped the Picea Engelmanni-Abies 

 lasiocarpa formation, on September 8 at 11:30 a.m. The obser- 

 vation was made in the general shade of the forest, not in the direct 

 shade of a tree trunk. The value was 5: 180. 



(6) THE PSEUDOTSUGA M:UCR0NATA-PICEA ENGELMANNI FORMATION 



{Hs^7>8) 



800 to 2700 



m 



9 



mingles with the Pinus scopulorum and P. Murray 



