542 JOURXAI. OF FORESTRY 



In the case of the forest taken as an example, the small and average 

 wood are in demand and always merchantable because of the proximity 

 of the factories which utilize them, notably the pulp mills. This small 

 and average wood, moreover, grows individually at a high rate ; they 

 guarantee the security of the forest against accidents, windfall, etc., 

 and assure, in a certain sense, its perpetuity. One can, then, without 

 fearing to make sacrifices, admit that each class must occupy equal sur- 

 faces. However, it is not necessary to allot a space to young fir with 

 a diameter less than 5 cm. — such can grow as an understory. 



There are, then, from 5 cm. to 45 cm., inclusive, nine classes, and the 



surface occupied by each will be per hectare '- niq. = i.iii 



square meters. 



(b) As regards number of trees in each class, there is presented the 

 niost important problem, namely, the most favorable spacing to give to 

 the trees. This spacing, which we will designate "normal," must be 

 both the chief guide in management and the "director of markings" ; 

 it is the cornerstone of the edifice, and it is by this notion of spacing 

 that one will succeed, without doubt, in finding the law of the separa- 

 tion into classes — a law which is being ignored absolutely, as Hiififel 

 has said at the silviculture congress. In agriculture and in horticulture 

 the law of the spacing of plants plays a very important role. . . . 

 In silviculture, also, a maximum yield evidently corresponds to a cer- 

 tain spacing; this is not entirely the maximum yield of gross material 

 given by each diameter class that it is necessary to find, but rather the 

 maximum yield in money per age class. 



In order to determine this "normal" spacing, we have proceeded with 

 two series of experiments. One determines the direct determination 

 by means of a plumb-bob of the crown (width) of trees which appears 

 "normal" from every point of view. The other depends on the stand, 

 as a whole, suitably selected. Here are some details on the second 

 series of experiments : 



When a stand is too open, the soil becomes covered with grass or 

 seedlings, and it then appears that the mature trees do not utilize all 

 the productive forces coming either from the soil or atmosphere ; when, 

 on the other hand, the stand is very dense, there will be on the soil 

 neither woody nor herbaceous undergrowth. In this case all the pro- 

 ductive forces are well utilized by the trees, but are divided among too 

 many stems ; it might even happen that most of them would only receive 

 enough to keep them alive and that they would not increase more than 

 a theoretical amount. . . . There is in this case a poor utilization of 



