412 Forestry Quarterly 



forestry proper, meteorology, geonomy, plant physiology, plant path- 

 ology, and zoology, and each department is in charge of a chief. 



The work as carried on by the Prussian organization is fairly 

 indicative of what is going on in other parts of Germany. Quite 

 naturally the problems which are taken up depend largely upon 

 local conditions. The work of the experiment stations as organized 

 under the International Association of Forest Experiment Stations 

 consisted, in 1904, principally of the study of the special ecology of 

 species, inquiring into their physiology, phaenology, relation to 

 .soil conditions, plant associates, manner of germination, and their 

 geographical distribution. 



In Sweden, where forest conditions are very much like those 

 which obtain in this country, the experiment station a few years 

 back was working upon ecological investigations of forest typCvS, 

 upon the races of pine and spruce, upon methods of thinning, yield 

 tables, upon methods of natural reproduction in selection forests, 

 upon brush removal, and upon methods of assisting natural repro- 

 duction by the preparation of the soil. 



The Determination of Light Values (72, 75) 



The determination of light values has, without doubt, received 

 more attention than has the measurement of any other habitat 

 factor. Light is one of the master factors affecting plant life and 

 is second only in importance to water. Both plant ecologists and 

 forest ecologists have contributed to this field. It is a problem that 

 has been given much study and investigation by some of the 

 German and Austrian experiment stations. Hence it is desirable 

 to at least mention the more important investigations on this phase 

 of ecology. 



It was Ingenhousz in the latter part of the 18th century who 

 first clearly perceived the tremendously significant interrelation 

 between light and life. It was he who showed that plants take 

 carbon dioxide from the air and give off oxygen. His great genius 

 saw more than this, however. Since oxygen is necessary for 

 animal life, and this gas, which is necessary for respiration, can 

 only be regenerated by plant life, it was clear that light is neces- 

 sary for animal life as well as plant life. From the time of that 

 important discovery dates practically all our knowledge concern- 

 ing the complex relation of light to plant life. 



