PERIODICAL LITERATURE 665 



In a comprehensive study L. Mattson gives 

 Form Classes the results of volume studies made by the 

 in Pine Swedish Forest Experiment Institute in Halsing- 



land in fully stocked stands of Finns sylvestris 

 lapponica of ages varying from 79 to 115 years. Mattson states that 

 the usual system of obtaining growth data in Sweden is by means of 

 felled sample trees. He, however, prefers long-time measurements on 

 permanent sample plots. His studies are designed to give some infor- 

 mation on the relative accuracy of the different methods of measure- 

 ments in fully stocked normal stands of pine, and were largely carried 

 on in three sample plots. 



The assertion is made that the "form factor" as a method of ob- 

 taining data is influenced by too many variables, such as density of 

 stocking, soil and site, etc., and that the increasing use of the "form 

 quotient" is a marked step forward, though he brands Schiffel's and 

 Maas' methods as defective. Mattson's argument is that as the d. m. 

 h. is an arbitrarily tixed point varying with respect to the d. b. h. in 

 trees of different heights, the form quotient will vary greatly with 

 trees of identical form but of different height, and cites as an illus- 

 tration the fact that in trees nine feet high the coincidence of the 

 d. m. h. and the d. b. h. will give an utterly absurd form quotient. The 

 Tor Jonson "absolute form quotient," which disregards the portion of 

 the trunk below the d. b. h., so that the d. m. h. is at the middle of the 

 stem above this point, is preferred as giving much more consistent 

 results even though it also is mathematically not entirely correct. 



For different form classes with unlike absolute form quotients, 

 Jonson has prepared taper tables calculated by means of Hojer's trunk 

 curve equation. In determining the form class of standing trees, 

 Jonson does not favor the Schiffel method based on the crown and 

 trunk relationship, but has deduced a "form period" method based on 

 Metzger's theoretical comparison between a tree and a "cubical" para- 

 boloid, which consists in determining the point in the stem where the 

 wind acting upon the crown produces the greatest bending moment. 



In the course of the investigation an incidental study of the relation 

 of the diameter at different heights and the thickness of the bark was 

 made. Measurements on standing trees were made with calipers, hyp- 

 someters, and Lof's extension caliper, by means of which the diameters 

 of the trees at a point six meters from the ground were readily and ac- 

 curately obtained. 



Detailed tables and curves graphically illustrating the results of 



