Apr. 14,19*3 
Physiological Requirements of Rocky Mountain Trees 163 
It is to be hoped that this distinction between the temporary qualities 
of seedlings which acutely influence natural reproduction and extension 
of ranges and the more fundamental qualities of the species which later 
control growth reactions and economic values may be clearly held in 
mind, since it becomes increasingly apparent as time goes on that the 
factors controlling reproduction must be considered as almost independ¬ 
ent of those controlling later growth. 
In a succeeding paper on this subject it is hoped principally to show 
to what extent the environmental conditions of the different forest types 
differ and, in the light of what we have so far seen, to weigh carefully 
the importance of each condition so that those conditions which are 
really essential to the success of a given species may be clearly under¬ 
stood. The practical application of these facts in forest management 
may then be shown, it is hoped, in more definite terms. 
LITERATURE CITED 
(i) Bates, Carlos G., Notestein, F. B., and Kepunger, Peter. 
1914. CLIMATIC CHARACTERISTICS OP POREST TYPES IN THE CENTRAL ROCKY 
MOUNTAINS ... In Proc. Soc. Amer. Foresters, v. 9, no. i, p. 78-94. 
(3)- 
1916. THE EPPECTS OP WIND. In Proc. Soc. Amer. Foresters, v. ii, no. 4, 
p. 443 - 444 * 
(3) - 
1917, THE BIOLOGY OP LODGEPOLE PINE AS REVEALED BY THE BEHAVIOR OP ITS 
SEED. In Jour. Forestry, v. 15, no. 4, p. 410-416. 
(4) -and ZoN, Raphael. 
1922 . RESEARCH methods IN THE STUDY OP POREST ENVIRONMENT. U. S. Dept. 
Agr. Bui. 1059, 209 p., 4 fig. List of references, p. 202-209. 
(5) Briggs, Lyman J., and Shantz, H. L. 
1912. THE WILTING COEPPICIENT POR DIPPERENT PLANTS AND ITS INDIRECT 
determination. U. S. Dept. Agr. Bur. Plant Indus. Bui. 230, 83 p., 
9 fig-. * pi- 
( 6 ) - 
1914. RELATIVE WATER REQUIREMENT OP PLANTS. In Jour. Agr. Research, v. 3, 
no. I, p. 1-64, I fig., pi. 1-7. Literature cited, p. 62-63. 
(7) Clements, Frederic Edward. 
1905. RESEARCH methods IN ECOLOGY, xvii, 334 p., 8$ fig. Lincoln (Nebr.). 
Bibliography, p. 324-334. 
( 8 ) - 
1907. PLANT PHYSIOLOGY AND ECOLOGY. XV, 315 p., 125 fig. New York. 
(9) - 
1910. THE LIPE mSTORY OP LODGEPOLE BURN PORESTS. U. S. Dept. Agr. 
Forest Serv. Bui. 79, 56 p., i fig., 6 pi. 
(10) - 
1916. PLANT succession: AN ANALYSIS OP THE DEVELOPMENT OP VEGETATION, 
xiii, 512 p., 51 fig., 61 pi. Washington, D. C. Bibliography, p. 473- 
498. (Carnegie Inst. Wash. Pub. 242.) 
(ii) Hilgard, E. W. 
1906. soils, THEIR PORMATION, PROPERTIES, COMPOSITION, AND RELATIONS TO 
PLANT GROWTH IN THE HUMID AND ARID REGIONS. XXvii, 593 p., 89 
fig. New York, London. 
(12) Kiesselbach, T. a. 
1916. TRANSPIRATION AS A PACTOR IN CROP PRODUCTION. Nebr. Agr. Exp. Sta. 
Research Bui. 6, 214 p., 24 fig., 4 pi. (in text). Literature cited, 
p. 209-214. 
(13) Moore, Barrington. 
1917. OSMOTIC PRESSURE AS AN INDEX OP HABITAT. In JouT. Forestry, V. 15, 
no. 8, p. 1010-1013. 
(14) Pearson, G. A. 
1914. A METEOROGICAL study op parks and timbered AREAS IN THE WESTERN 
YELLOW-PINE PORESTS oP ARIZONA AND NEW MEXICO. In Mo. Weather 
Rev., V. 41 (1913), no. 10, p. 1615-1629, 9 fig. 
