230 JOURNAL OF FORESTRY 



be possible to organize an experiment in which all factors of growth, 

 except light, should be favorable, while light should be at its minimum. 

 The experiment can be arranged something like this : 



In a nursery bed in which the soil is fresh and fertile, raise or plant 

 out seedlings of several light-needing and shade-enduring species, say 

 larch, Norway pine, spruce, and white oak. Divide the bed into 

 several parts, each containing rows of all of the four species, and cover 

 three such parts of the bed with ordinary boxes from which the sides 

 facing north have been removed. The light would thus reach the 

 seedlings only from the north. Beside the three boxes covering three 

 lots of the different seedlings the rest of the bed should be used as 

 control lots for comparing them with each lot covered w^ith the boxes. 

 The light under the boxes in the middle of them should be about one- 

 twentieth of the daylight or at any rate it should be of such low light 

 intensity as would prevent the seedlings, even of the most tolerant 

 species, from growing naturally in the forest. The seedlings nearest to 

 the open on the north side would receive, of course, most of the light, 

 and those farthest removed from it the least. The factor which will 

 be at its minimum will be light. The soil under one box should be 

 watered occasionally when it gets too drj'. The soil under another 

 box should be watered more often, while the soil under the third box 

 should be watered with solutions containing a complete fertilizer. If 

 improvement in the soil fertility can compensate for deficient light, 

 then the plants under the third box should have a greater survival and 

 better development than in the other two boxes. This difference should 

 be particularly greater in the case of the light-needing seedlings than in 

 the shade-enduring ones. If, on the other hand, the mortality of the 

 seedlings in the third box is as great, or even greater as I expect it 

 will be, than in the two other boxes, then the conclusion would seem to 

 be that soil fertility cannot take the place of deficient light and that 

 the general belief that fertility of soil increases the tolerance of trees 

 must be based on faulty observations. There is no doubt that there are 

 reliable observations which showed that trees growing in the shade 

 have often improved in growth with the improvement in the fertility 

 of the soil. It is questionable, however, if in such observations there 

 has ever been made an attempt to ascertain whether it was not the 

 fertility or the moisture of the soil that was farthest from the optimum 

 for forest growth than light. If it were soil conditions that were below 

 the optimum, then it is only natural that the growth should have- im- 



