1918] CURRENT LITERATURE 77 
in the ground water tends to promote nitrification. He points out that by 
proper forest management the formation of nitrates =e be accelerated and a 
decided increase in timber production obtained. 
In a second article** he investigates the problems of the regeneration of 
conifer forests, with particular reference to the transformation of nitrogen, for 
it appears that while trees of pine and spruce often grow in forests where no 
nitrate formation is taking place, the raw humus developed beneath their dense 
shade does not prove a good soil for the rapid growth of their seedlings. It 
seems from experimental evidence that nitrogen transformation in such soils 
may be initiated and accelerated by the introduction of light through cutting, 
by burning the surface, or by stirring the surface soil. Decaying timber seems 
to favor nitrogen transformation, and this may tend to account for the observed 
abundance of conifer seedlings growing upon fallen logs. 
In mixed conifer stands, especially where the herbaceous undergrowth is 
good, nitrate formation is, in contrast, rather active; so much so in many 
instances as to induce such a rank growth of herb and grass vegetation in clear- 
ings as to crowd out conifer seedlings. ‘These and other data should help to 
explain to the ecologist many phenomena of secondary succession, while from 
the same data the forester should receive guidance for the formulation of a 
policy of forest management that will favor the formation of the amount of 
nitrogen best suited to the regeneration of the forest. 
The value of these excellent papers is increased by an abundance of tabu- 
os data, ae Maes freely illustrated, and by extensive bibliographies.— 
Eo. D. Fuiy 
Mechanics of movement in insectivorous plants.—Two recent papers on 
this aya . Brown’ and by Hooker,” have supplied some interesting 
information. Although different plants were used, the results are comparable 
in many respects. Both investigators find that the bending is accompanied by 
an extension of the cells on the convex side, which soon becomes fixed by growth; 
that there is little or no change of size in the cells of the concave side; and that 
unbending is accompanied by growth on the concave side. Hooker finds the 
Osmotic pressure of the cells on the convex side of bending tentacles less than 
that on the concave side, and this decrease is proportional to the increase in 
the length of the cells. He finds no changes in permeability and concludes that 
the increased size of the cells is due to decreased elasticity of the cell walls. 
“ HESSELMAN, Henrik, Om vara ee a pa sa 
peterbildningen i i marken och dess betydelse f ng (with persis 
ee ares a fran Statens Se pknin. ‘Haft 13-14. penny pls. 15. 
gs. - 
Own, Wa. H., The mechanism of movement and the duration of the effect 
of 2 cheba in the levies of Dionaea. Amer. Jour. Bot. 3:68-90. 1916. 
* Hooker, Henry D., Jr., Mechanics of movement in Drosera rotundifolia. 
Bull. Torr, peg Club 44: 389-403. ted be 
