Periodical Literature. 93 



A series of measurements in planted dense spruce stands gave 

 on an average lower intensities than 60 to 70 lux. 



A stand of natural regeneration mixed with fir gave in the aver- 

 age 74 lux; a 90 to 100-year-old stand of same description with 

 soil cover of needles and occasional Hypnum and without any re- 

 production, gave 84 lux; a 75-year-old spruce stand with a soil 

 cover of Oxalis, Hypnum and occasional Carex, gave 56-88 or 

 72 lux in the average. 



A series of measurements in stands with natural regeneration 

 developed the difference in relative shade-endurance of spruce and 

 fir. Fir reproduction was found to come in with 95 lux and could 

 persist with 95 to 105 lux, while spruce for permanent success re- 

 quired at least 120-140 lux. 



That other than light influences play a part, the author well re- 

 cognizes, and cites various examples. 



Most interesting are the measurements of light intensities 

 found under various degrees of thinnings. Here, average figures 

 would be misleading, hence the detail of a long series of measure- 

 ments and their ranges are needed to give an insight. The ex- 

 perimental areas at Grafrath were used, the measurements made 

 in medium strong daylight. 



In the severely thinned stands the minimum was 88 lux, the 

 maximum 235, and the higher intensities were more frequent 

 than the lower, half the number of measurements lying above 112 

 lux. The medium grade shows a range of y6 to 168, half the mea- 

 surements lying between 84 and 102. The light thinning grade 

 shows a range of 68-108, and more uniform conditions, over 80 

 per cent lying between 68 and 80 lux, and rarely any over 120 lux. 

 From three different series of measurements the author averages 

 the relative intensities for the three degrees of thinnings as 80.4, 

 96.4, 125 lux respectively. The series given permit the recogni- 

 tion of a regular lawful progress of light intensity from the clos- 

 ed, planted stand to the severely thinned and open stand. 



Highly interesting are the reflections which the author makes on 

 the practice of thinnings. He points out that natural regenera- 

 tion and artificial reproduction differ in their continued effects 

 on the stand. In the natural regeneration, the plants differ con- 

 siderably in age, standing room and inherent growth capacity, 

 hence an early differentiation of the favored individuals, the 



