10 July, 1917.] Weeds. 429 



Destroyiu,^ weeds by the use of arsenical preparations is of very 

 little value except for tlie purpose of freeing paths, &c., from vegetable 

 growths. The use of arsenic against deep-rooted |)ereunials is absolutely 

 useless unless used in such quantities as to completely destroy the 

 fertility of the land. Various tests were carried out at Briglu with all 

 kinds of arsenical preparations for the destruction of St. John's Worb. 

 These applications were found to be immediately fatal to all growth 

 above the surface, but did nothing to prevent fresh growth being 

 pushed up from the strong root system below. When arsenic was used 

 ati siifficient strength to destroy these roots it was found to completely 

 destroy the land for two or three seasons and render it useless for the 

 growth of plants. A much better weed-killer for voung plants is crude 

 petroleum or kerosene. This, when sprayed over them, destroys the 

 plants, but leaves no ill-effects on the soil. 



Salt is an effective weed-killer and one that in manv parts of 

 Victoria improves the fertility of the land. Salt is a deliquescent sub- 

 stance which extracts water from the moisture in the atmosphere and the 

 surrounding objects that it comes into contact' with. Thus when 

 applied to succulent plant tissues it^ draws water from them, and 

 produces an effect similar to scorching. Thus it is of special value 

 when applied to the roots of weeds after they have been cut or bruised, 

 as it draws the sap reserves of the plant to the surface, where it is then 

 evaporated. 



Much has been said about cultivation for the suppression of noxious 

 weeds. This is easy when dealing with annuals that occur on arable 

 lands, but it is useless to talk about cultivation on lands unfit for 

 cultivation either on account of their contour or composition. If lands 

 are steep, or have stony outcrops, they may be first-class grazing lauds, 

 yet. totally impossible to bring under the plough, and it is to this class- 

 of land that the menace of the introduced weed looms large. If lands 

 can be brought under the plough, and good cultivation given at short 

 intervals, the most obstinate plant can be destroyed, for if the leaves 

 are kept from forming the crude sap ^ent up by the roots cannot be 

 elaborated, and the planti starves to death, as sap is of no use to a plant 

 until it has been dealt with by the leaves, and returned as plant- 

 building material. The mistake is often made in allowing too great an 

 interval between the stirrings of the soil, with the result that leaves 

 are formed and pushed through the surface of ground in the short time 

 between the cultivations, with the resulti tliat sap is elaborated and 

 the plants again renew their strength. Unless cultivation is frequent 

 it cannot' kill such plants as St. John's Wort, Canadian thistle or black- 

 berries. 



The reason why so many weeds are troublesome on grazing lands is 

 not always so much on account of their greater vitality or powers of 

 reproduction, but in the fact that, on account of their less attractive- 

 ness and rejection by stock, they have an unfair advantage over the 

 more succulent herbage, and v.hile the latter is being eaten down close 

 the weed is allowed to grow and develop its seed. Instances of this 

 can be noticed on railway enclosures where Kangaroo grass ia usually 

 plentiful, yet outside the fence, on account of close feeding by stock, 

 it has almost' disappeared. This grass, providing stock is kept from it, 

 can completely suppress St. John's Wort, but as soon as stock and 



