90 Forestry Quarterly 



40° F. (a) Days with frost, and (b) days without frost. Cool 

 days, with an average daily temperature from 40.1° F. to 50° F. 

 (a) Days with frost, and (b) days without frost. Moderate days, 

 with an average daily temperature from 50° F. to 59° F. These 

 are the days of moderate growth. Warm days, with an average 

 daily temperature from 59" F. to 72° F. These are the days of 

 most vigorous growth and the ripening of fruits in temperate 

 latitudes and altitudes. Hot days, with an average daily tempera- 

 ture above 72° F. (a) Dry, hot days, which act depressingly upon 

 vegetation; (b) moderately humid hot days, which expedite the 

 ripening of southern fruits; (c) humid hot days, which produce a 

 tropical growth of plants of the humid subtropical region. 



Similar classifications might be made for the humidity of the 

 air, precipitation, snow cover, sunshine, soil temperature and soil 

 moisture. All but the last two could be obtained from the data 

 given by the ordinary weather station. The trouble with appl)7ing 

 such data to forest trees, however, is that stations of the Weather 

 Bureau are not located in forest regions. 



Meteorological Observations in Connection with Botanical Geography, Agri- 

 culture and Forestry. Monthly Weather Review, April, 1914, pp. 217-223. 



Dr. Knuchel of the Swiss Experiment 

 Measurements Station reports on a series of measurements 

 of of light in forest stands through four 5^ears 



Light to determine answers to the three questions, 



to what degree different species in single 

 specimens and in stands retain light in their crowns; what color 

 composition the light passed through the crowns has; what influ- 

 ence the light in the interior of a stand has on soil flora and regen- 

 eration. 



First discussing the history and methods of measuring light, 

 exhibiting their defects, especially since under crown cover the 

 quality of the light varies as well as the degree, necessitating 

 consideration of the various spectral fields, he describes a new 

 spectrophotometer which was used in these investigations, and the 

 method of procedure. The instrument is bulky, heavy and 

 expensive, but works accurately, and can be considered standard 

 (by which to compare efficiency of simpler methods of measure- 

 ment) and capable of securing basic knowledge of light quality. 



