PERIODICAL LITICRATURE 725 



This article is the result of extensive stem- 

 Forui-variations form studies carried on by L. Mattsson, of the 

 of Swedish Institute of Experimental Forestry, on 



Larch material taken from the large collection of sample 



trees of European and Siberian larch of the In- 

 stitute. These trees are measured in sections of one meter, with the 

 first measurement at 0.5 m. above stump. The diameter of the stump 

 and at breast height (1.3 m.) and the thickness of bark at all sections 

 is also measured. Mattsson divides the stems into form classes and 

 height classes, and works out average values of the diameter quotients 

 at the different cross-sections on the stems for each of these classes. 

 The height classes were based on the unit length of one meter and the 

 form classes were obtained by means of the Janson "absolute form 

 quotient" — that is, the diameter at the middle of the stem above breast 

 height divided by the diameter at breast height. The values for each 

 form-height group were plotted on cross-section paper and the diameter 

 quotients read off on the rounded curve at every 10 per cent of the 

 height of the stem above d. b. h. From these data a general taper series 

 was w^orked out applicable to all trees of a certain form quotient and 

 illustrating the form of the stem inside bark and above d. b. h. In the 

 final series the influence of root swelling was eliminated. 

 Among the important results of the investigations are: 

 (i) The general construction of the stem of the two larch species 

 examined is quite the same. 



(2) The taper series obtained by Mattsson agrees almost entirely 

 with the taper series worked out by Professor Janson for Scotch pine. 



(3) The form-class variation within a stand is very great. The 

 amplitude does not seem to vary with any particular character of the 

 stand. 



(4) The form-class curve within a stand shows a sligiit drop with 

 increasing d. b. h. 



(5) The mean form class of the stand is very closely related to the 

 mean height. 



Where any deviation from the form class determined by the mean 

 lYfeight can be demonstrated, this deviation can be explained as due to 

 the density of the stand during the period of best growth. The mean 

 form class of a stand is therefore to be determined with sufficient ac- 

 curacy for all practical purposes from the mean heigiit of the stand. 

 Should greater accuracy be desired, the density during the time of 

 growth, determined by comparing the mean diameter of the stand ob- 



