Studies on the Production 

 of Matter in Light- and Shadow-Plants. 



1. Introduction. 



few years ago I carried out some investigations on the 



behaviour of forest trees to light (1910 p. 1). On that occasion 

 I also made some experiments on the rate of the production 

 of matter by young forest trees in relation to light (1. c. p. 56). 

 During the summers 1911 — 1917 I made some further investi- 

 gations on this question in other plants. The experiments were 

 partly carried out in Vejen, Jylland, partly at Maglemose in 

 Gribskov near Hilleröd. 



The problem especially to be elucidated through these in- 

 vestigations is how much organic matter certain plants of diffe- 

 rent types can produce per unit of time; the percent production 

 of matter as I would call it. Let us begin with a definition. By 

 the percent production of matter I mean the amount of dry 

 matter produced in unit time, calculated in percent of the dry 

 matter in the plant in question at the beginning of the experi- 

 ment. When a plant with a content of 100 g dry matter pro- 

 duces in 24 hours 20 g dry matter, the daily percent production 

 of matter is 20°/o. In planctology similar conceptions are used. 

 For instance Gran (1908 p. 1) finds that about 20 °/o of the Pe- 

 ridineae in the sea divide during a night in Septb. ; this figure 20 

 indicates the »speed of increase« for the organism in question. 



In what follows we shall enquire how this percent produc- 

 tion of matter can be estimated. 



As may easily be seen, the question of the production of 

 matter is very complicated, since all the factors acting on the 

 plants influence also the intensity of the production of matter; 



By 



P. Boysen Jensen. 



15* 



