214 INSECTICIDES, FUNGICIDES, AND WEED KILLEKS. 



enable the work to be controlled owing to the blue spots which they 

 leave on the organs touched. In spite of these drawbacks blue vitriol 

 is still used in 25 per cent solution in Le Tarn, owing to the low 

 cost of the spraying. To give adherence to blue vitriol Trabut advises to 

 add mucilaginous substances to its solutions ; the mucilage extracted 

 from the prickly pears of the Barbary fig-iree, and galipot, a dry 

 resin which exudes the whole length of the Algerian pines, previously 

 dissolved in carl)onate of soda. The galipot soap bouillie has the fol- 

 lowing composition : galipot, 1 lb. dissolved in ^ lb. of soda crystals ; 

 blue vitriol, | lb. ; water, 10 gallons. The bouillie with the Barbary fig 

 mucilage basis is made thus : 3-5 lb. of the prickly pear of the Barbary 

 fig are cut up and macerated in water. After extraction of the muci- 

 lage i-^- lb. of blue vitriol is added and the mixture made up to 10 

 gallons. These preparations effect a saving of 50-80 per cent of blue 

 vitriol and are cheaper in Algeria. They are to be recommended in 

 countries where rain is rare, and where the number of sprayings neces- 

 sary do not exceed those with bouillies. Viala's, Pichi's. and Eumm's 

 experiments show that mildew^ may be contended against by spraying 

 round the stocks with blue vitriol solutions ; this salt w^ould therefore 

 possess serious advantages over bouillies. Unfortunately the doses 

 required to obtain immunity are such that there can be no question of 

 employing this treatment on the large scale. From experiments of 

 Chmjelewsky it follows that blue vitriol has a deadly action on fructi- 

 fication. Beach and Bailey also found that it was deadly to pollen ; 

 0-02 per cent solutions lower its vitality, and it is killed when it comes 

 in contact with 0-5-2 per cent solutions. If the flower be open for 

 some days only before the treatment the action of the blue vitriol is 

 less injurious. Spraying with blue vitriol should thus be avoided 

 during flowering if it is not desired to do great damage to the crop. 



Use of Mixtures containing Blue Vitriol. — As the vine-grower 

 already was accustomed to disti-ibute flowers of sulphur wnth a bellows 

 to contend against oidium, the operation of treating the mildew would 

 have been greatly simplified if it had been possible to use blue vitriol 

 in a pulverulent form mixed with sulphur. A great number of analo- 

 gous mixtui-es have been compounded in different countries. They 

 either contain blue vitriol mixed with powdered inert bodies, or are the 

 elements of cupric bouillies with or without sulphur. With some rare 

 exceptions, the adherence of these is much less than that of cupric 

 bouillies which renders them liable to be carried off" by the wnnd and 

 by the first rain. It is also necessary to apply them in the dew of the 

 morning, so as to render them a little more adherent. It will be seen, 

 therefore, that these preparations cannot be regularly used except in 

 moist countries, and that those which contain sulphur cannot produce 

 on the oidium the categoric effect of sulphur alone used at a full heat. 

 To increase the adherence of blue vitriol on the leaves it has been 

 mixed with substances like talc, powdered coal, alumina, sulphate of 

 lime, and sugar, or it has even been dehydrated and reduced to an 

 impalpable powder by calcination. The latter preparations are the 

 only ones of any real use in cei-tain circumstances. Powders consisting 

 of pulverized blue vitriol and various othei' bodies, mixed by grinding,. 



