xoTKS 885 



is shown graphically by shading those areas where semicircles for a 

 given factor overlap. For example, with temperature, Abies is above 

 (north of) Acer, but the lower half of the Abies temperature semicircle 

 overlaps the upper half of the Acer temperature semicircle. 



The temperature diagram includes fifteen species and is fairly re- 

 liable, as far as the reviewer can tell. Populus balsamtfera is given the 

 greatest range, with Bctiila papyifcra only slightly less and a little less 

 to the north. Picca niariana and Picca canadensis are equal in extent 

 of range, with the former a little further north. Pinus banksiana is 

 placed a little to the north of Abies balsamea, but with a somewhat 

 narrower range. This might be questioned, in view of the southern 

 extension of Pinus banksiana along the Rocky Mountains. 



The diagram for water requirements gives thirteen species, some of 

 which are not found in the temperature diagram. Larix amencana is 

 given by far the greatest range, including all the others, except for 

 insignificant areas of the Populus tremuloidcs and Pinus banksiana 

 semicircles in the dry end of the scale. The relative position of the 

 remaining species appears to be about that which one would expect, 

 with the possible exception of Tsuga canadensis, which is placed below 

 Fagus amencana, Acer sacchariim, and Picea canadensis in water re- 

 quirement. 



It is when we come to the diagram of soil requirements that Hutch- 

 inson fails. He covers only the physical properties of soils, chiefly as 

 influenced by the proportion of humus in mixture. This is due to 

 Hutchinson's acceptance of the dogma that the composition of the soil 

 (the chemical elements which it contains) is of itself unimportant. 

 The diagram is therefore limited to "soil development." By this he 

 appears to mean the degree of disintegration and proportion of humus, 

 starting with rock particles devoid of humus and ending with a soil 

 "well drained, well aerated, and containing a relatively large amount 

 of humus intimately mixed with the rock soil," which he terms "mature 

 soil." The conception of soil development is sound. But Hutchinson 

 deliberately ignores the fundamental principle that different rock for- 

 mations do not develop similar soils. They may, and often do", develop 

 soils which are similar in physical properties ; but similar physical 

 properties do not mean similar fertility or the ability to support the 

 same type of vegetation. Burd^ has found "great variation in yields 

 and water extracts between individual soils in a (physical) type which 

 is probably unusually uniform." Burd's w'ork is a striking laboratory 



" John S. Burd : "Chemical criteria, crop production, and physical classification 

 in two soil classes." Soil vScience, Vol. 5, No. 5, pp. 405-419, May, 1918. 



