564 EXPERIMENT STATION RECORD. 



1901, 2.3 per cent; in 1902, 5.2; in 1903, 4.5, and in 1904, 3.2. On the irrigated plat 

 the increment percentage in 1901 was 5 per cent; in 1902, 7.4; in 1903, 7.1, and in 

 1904, 5.5. 



These figures show an increased increment of about 10 per cent in favor of irriga- 

 tion. The favorable effect of irrigation was noticed the first year, especially with the 

 lower class trees. 



Forest irrigation experiments, A. Cieslar (Centbl. Gesam. F<>r*1ir., si (1905), 

 No. 5, pp. 195- 211, figs. 2). — An account of irrigation experiments with young stands 

 of white and Austrian pine and spruce during the period 1901 to 1904, inclusive. 



From May to September of each year from 38 to 44 irrigations were given. The 

 dates of each irrigation; the character of the year as regards precipitation, etc.; the 

 number of trees which lived on the different plats, and the growth they made are all 

 shown in detail. Irrigation proved especially efficient in the case of spruce. White 

 pine seemed to be injured by irrigation except in the one very dry season of 1904, 

 when marked results in favor of irrigation were noted. Austrian pine appeared not 

 to be injured by irrigation in 1903, and was greatly benefited in 1904. 



In other observations the author notes that Austrian pine withstands drought 

 much better than white pine, and in dry situations should be selected for planting 

 in preference to white pine. 



The dead cover of forests and nitrogen, Horxbergek (Ann. Sd. Agron., 2. ser., 

 10 (1905), I, Xo. .'. [>i>. 2.'f)-Mo).— The author briefly reviews the work of E. Henry 

 (E. S. R., 16, p. 444) relative to the decomposition of dead leaves in forests and the 

 fixation of atmospheric nitrogen, and gives the results of his own experiments con- 

 ducted along the same lines. 



The zinc boxes used in the author's experiments were 20 cm. square and 10 cm. deep. 

 Holes were punched in the bottom so that water could escape and the bottom was 

 covered with filter paper. Six of the boxes used contained a small amount of sand- 

 stone in the bottom. The leaves used in the experiment were those of oak, beech, 

 pitch pine, ash, hornbeam, and acacia. 



They were gathered in the fall and placed on screens and covered over, with paper 

 to keep the dust from them until they were needed in the experiment. Part of the 

 leaves were then analyzed and the remainder put in their respective boxes and left 

 in the open from February 0, 1903, to February 6, 1904, exposed part of the time to 

 the rain and all of the time to the air. At the end of the year the leaves in all of the 

 boxes were again analyzed with reference to their nitrogen content. 



In all except 2 cases the total nitrogen content of the leaves had decreased instead 

 of increasing, as was the case in Henry's experiments. Even in the 2 cases in which 

 there was an increase the increase was so slight as to be within the limits of analytical 

 error. 



Observations on the preceding 1 memoir, E. Hexry (Ann. Set. Agron., 2. ser., 

 10 (1905), I, No. 2, pp. 231-236). — The author reviews the above article by Dr. Horn- 

 berger on the decrease in nitrogen content of decayed forest leaves, and argues that 

 the results of the experiments under the conditions in which they were conducted 

 were not other than what might have been expected. 



In gathering the leaves and allowing them to dry before the experiment began, the 

 uerminative ability of the micro-organisms originally existing on the leaves in the 

 forest would be largely lost, and the material would therefore become nearly sterile 

 and not able to function as normal dead leaves in the forest. In order to secure 

 results of value it would be necessary to carry on the experiment under conditions 

 exactly as they exist in large forests. 



The recent work of a number of other investigators is cited to show that nitrogen- 

 fixing bacteria really assimilate the free nitrogen of the air in the decomposition of 

 forest leaves. 



