*68 BOTANICAL GAZETTE [august 



Contraction of roots. — Miss Church 15 has studied the contraction of 

 roots, and while she thinks some of Rimbach's conclusions were not justified 

 by his facts, she thinks the following can be accepted: " (i) roots do shorten; 

 (2) the parenchymous tissues of the root are the seat of activity; (3) the cork 

 and the vascular trace are passive; (4) the cork is ultimately crushed; (5) there 

 is a region where one can see wrinkling and measure shortening, a second region 

 where no wrinklings are visible yet one can measure shortening, and an un- 

 changed region (Rimbach) ; in dicotyledons the trace becomes visibly curved 

 inward and outward in a wavy fashion, while in monocotyledons the vascular 

 bundles remain practically straight (DeVries)." — Wm. Crocker. 



Energy of biological processes. — Lixhart 16 , in a preliminary paper, has 

 called attention to the almost neglected field of study of the energy relations 

 in biological processes. By employing similar methods to those recently 

 used in attempts to base chemical reactions on thermodynamic principles, 

 Lixhart hopes to be able to measure the energy values of various biological 

 processes. The heats of combustion of the nutrient materials must be known. 

 With these data, and the entropies of the substances involved, it is possible 

 by thermodynamic equations to compute the free energy from a reaction. 

 The energy available to Azotobacter grown on mannite was thus calculated. 

 The amount of NH 3 fixed by Azotobacter in consuming a certain amount of 

 mannite was found to represent only about 1 per cent of the energy value of 

 the mannite. — J. R. Magness. 



Heat treatment of seeds. — Atanasoff and Johnson 17 



carried 



« Church, Margaret B., Root contraction. Plant World 22:337-340. 1919. 



16 Lixhart, G. A., The free energy of biological processes. Jour. Gen. Physiology. 

 V. 2:247-251. 1920. 



17 Atanasoff, D., and Johnson, A. G., Treatment of cereal seeds by dry heat. 

 Jour. Agric. Res. 18:379-390. 1920. 



t 



18 Keen, B. A., The relation existing between the soil and its water content. 

 Jour. Agric. Sci. 10:44-71. 1919. 





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parasites. They emphasize the necessity of applying this method only to 



high quality, well dried seeds. They could thus dispose of bacterial blight of 



barley and of oats. The wheat scab (Gibber ella soubinetii and Fusarium spp.)> | 



primary infections only, and spot blotch of barley (Helminthosporium sativum) 



are practically eliminated by dry heat treatment. The Helminthosporium 



blotch of oats, as well as loose smut of barley and smuts of oats, were 



markedly reduced by such treatment. In all of these cases, of course, the 



germination was not materially injured. — Wm. Crocker. 



Soil moisture. — Keen 18 gives an excellent discussion of the latest litera- 

 ture on the mechanics of soil moisture. — Wm. Crocker. 





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