POEESTBT. 343 



author takes exception to the opinion advanced by Metzger « that the trunk and 

 branches of trees are developed as pillars of equal resistance against wind 

 pressure, and conclades from his own observations that the development of any 

 particular form in a tree should be regarded as the attempt to establish a shaft 

 with equal -R-ater-carrying capacity and that the form of a tree is dependent 

 upon the combined influence of all climatic factors acting on the turgor power 

 of the tree. The physiological action of light through which transpiration and 

 assimilation are mainly promoted should be regarded as the measuring factor 

 for the form of the tree rather than the mechanical action of ^and. 



Planning experiments on the influence of stand density as well as vari- 

 ous silvicultural practices upon the moisture and humus content of our 

 forest soils from a practical standpoint, D. Tiemann {AUg. Forst v. Jagd 

 Ztg., 89 (1918), May, pp. i53-J65).— After pointing out the interdependence of 

 light and soil as factors in the development of timber stands, the author submits 

 outlines of some 20 experimental projects dealing with stand density and soil 

 improvement, the solution of which it is believed, will be of great value to the 

 forester. 



Winter stoi-age of acorns, A. Oppeemann (Forstl. Forsogsv. Danma^rk, 4 

 (191S), No. 2, pp. 127-133, fig. 1).—A number of small samples of acorns in- 

 tended for breeding purposes were stratified iu sand and stored over winter in 

 a sand pile. The unusually severe winter temperature, which at one time fell 

 as low as —20° C, resulted in the destruction of many of these samples by 

 frost. A subsequent examination of the samples showed that the acorns which 

 were allowed to dry out too much before being stored were more seriously 

 damaged. Hence the author concludes that a certain degree of moisture is 

 requisite to the resistance of acorns to frost. This opinion appears to be sub- 

 stantiated by the fact that many acorns which were left unprotected in the 

 open under relatively moist conditions sprouted in the spring notwithstanding 

 the severe winter temperatures. 



Although no data were secured relative to the degree of frost to which the 

 different samples were submitted and the amount of injui-y which occurred in 

 each case, the results of other obsei-vations indicate tiiat many acorns are 

 killed when submitted to a temperature of —7*. 



A way to improve the qiiality of pine seed, Busse (Ztschr. Forst u. 

 Jagdtc, Ji5 (1913), No. 5, pp. SOO-SIS). — The author here maintains that the 

 absolute weight of specified samples of seed is one of the factors in determining 

 the qualitj' of pine seed. By the use of a centrifugal machine he has been able 

 to separate samples of pine seed into 3 separate weight classes. In a germina- 

 tion test of the 3 separate grades very littie difference in the genninating power 

 was noted, the small inferior seed giving slightly higher results. On the other 

 hand, the root development of the seedlings decreased directly with the grade of 

 the seed. 



In conclusion the author briefly describes the grading of seed with a fan 

 separator as conducted at a seed house in Regentin-on-the-Frankfort. 



The growth, of red pine in Ontario, A. H. D. Ross {Forestry Quart., 11 

 {1913), No. 2, pp. 160-111, ftg. 1). — This comprises height, diameter, nnd vol- 

 ume data based upon stem analyses and measurements of red pine growing in 

 the Nipissing region, Ontario. 



Observations on the inception, season, and duration of cambium develop- 

 ment in the American lai'ch (Larix laricina), L. Knudson {Bui. Torrey Bat. 

 Clnh, JfO {1913), No. 6, pp. 271-293, pU. 2, figs. 5).— This paper is based upon 



» MiiiMlener Porstl. Hefte, 1893, No. 3, p. 55 ; Naturw. Ztscbr. Forst a. Landw., 6 (1908), 

 No. 5, p. 249. 



