NOTES AND ABSTEACTS. 



181 



of dust containing tarry particles on the leaves. Private gardens 

 along the tarred routes also suffer considerably by the same cause. 



G. T. D. 



Tarred Streets, Damagre to Plants by Dust from. By F. 



Fischer {Oestr. Gart. Zeit. vol. vi. pt. viii. pp. 291-6). — Trees and 

 bushes are damaged by the vapour from hot tar. Where cold tar is 

 used on the roads no injury is caused to vegetation. — S. E. W. 



Tea-root Diseases. By T. Fetch (Circ. and Agr. Jour. Roy. 

 Bat. Gard. Ceylon, v. pp. 95-114; 1910). — Five separate root-diseases 

 at one time confused under that caused by Rosellinia are described and 

 distinguished. They are produced respectively, by Ustulina zonata, 

 Hymenochaete noxia, Poria hypolateritis, Botrydiplodia theobromae, 

 Rosellinia bothrina. — F. J. C. 



Temperature coefficient of the Duration of Life of Barley 



Grains. By T. H. Goodspeed {Bot. Gaz. pp. 220-4, March 1911). 

 Fifteen thousand seeds were used, aflid 300 separate determinations 

 were made. The duration of life was taken to be the time in minutes 

 for which a given temperature must act in order to inhibit subsequent 

 growth. This was found for all temperatures from 55° to 70° 0. The 

 coefficient is about 11 for a temperature interval of 10°. At 55° dura- 

 tion of hfe was 65 to 70 minutes, and at 70° 1| to 2 minutes. 



G. F. S.. E. 



Thistles, The Control of Quack Grass and Canada. By A. L. 



Stone (U.S.A. Agr. Exp. Stn., Wisconsin, Circ. 19, July 1910). — Pre- 

 ventive measures have not been sufficient to check weed increase on 

 Wisconsin farms, so this circular describes remedial measures on the 

 lines of eradication. 



On large areas persistent ploughing ^nd harrowing either with a 

 crop or, better still, on fallow is the best means of destroying both 

 pests. 



On small areas, covering the ground with heavy paper after cutting 

 the weeds will eradicate them, providing the ground is level; otherwise 

 close cultivation will answer the same purpose. 



Canada thistles, but not quack grass, can be killed by a good 

 stand of alfalfa, and for scattered plants, or very small patches, carbolic 

 acid or gasoline can be used. Salting is a good plan, especially if cattle 

 Are pastured on the field, as they will destroy the thistles to get at the 

 salt.— C. H. L. 



Thrips, The Greenhouse. By H. M. Eussell {U.S.A. Dep. 

 A^r. Bur. Entom., Bull. 64, pt. vi. ; August 1909; 3 figs.).— The 

 damage caused by the greenhouse thrips (Heliothrips haemorrhoidalis 

 Bouche) is confined to the foliage of ornamental plants. Adults and 

 larvae (both obtain their food by puncturing the epidermis of the leaf, 

 and after lacerating the tissue they suck out the plant juices at the 

 point of attack. They then transfer their attentions to another part 



