326 Forestry Quarterly. 



strike the plane. A vertical from the point of observation forms 

 with the rays the zenith angle (z), which complements M to a right 

 angle, hence M=90-s, and the intensity of the light is expressed 

 by sin (90-s). A formula well known to astronomers makes cos 2 

 =zsin y sin 8 -\- cos y. cos 8 cos t, when y is the geographical lati- 

 tude, t the sun's time in degrees, 8 the inclination of the sun depend- 

 ent on the season and, together with the sun's time, to be found for 

 any moment in an astronomical calendar. The last two formulas 

 give the intensity of the light, and the calendar its duration, begin- 

 ning and end. 



The light intensity and duration was then established for 

 a number of sample plats of 1 qm located at varying distances from 

 the standing timber, and 5 m distant from each other. The influ- 

 ence of the different intensities on the natural regeneration was 

 determined by the average number of seedlings per ha. ; the influence 

 on sowings by counting germinated plants on 100 spots, computing 

 the germination percent, and the percent, of successful spots; the 

 influence on planting by determining the number of plants persisting 

 after a given time. 



From the large amount of observations recorded in 18 tabulations 

 the following conclusions are drawn: The success of natural re- 

 generation of pine depends on the degree of light. Side shade 

 favors it and reduces loss in sowings and plantings. The explana- 

 tion lies in the reduced temperature and reduced loss of moisture 

 from the soil. To secure good reproduction the width of the strips 

 should not exceed 60 m. The strips in echelons are very much bet- 

 ter seeded than those in series. 



Ueber Kulissen und aneinander gereihte Schlage, Allgemeine 

 Forst- und Jagdzeitung. Sept., 1906, p. 306. 



A long and most suggestive article by 

 Tending Schiff"el does not pretend to bring anything 



the new but analyzes critically and exhaustive- 



Crop, ly on the basis of empiric and scientific bio- 



logical knowledge silvicultural questions on 

 which opinions diverge. Such systematic presentation of the prin- 

 ciples by such an authority, even though elementary, is worth while 

 devoting space and time to brief fully. 



Under "factors of the form of stands," the author discusses the 



