80 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



will be seen that this amount of toxic gas, if not utilized, may carry 

 devastation to great distances. Many observations have been made 

 on this point, and it is found that near (such) factories the leaves of 

 the fir (? spruce) fall, those of the pine and larch, more resistant, only 

 brown at the point, and the trunk blackens; conifers, in general, do 

 not i-esist long. Deciduous trees, fruit trees, among others, lose their 

 leaves and do not produce fruit, because the sulphurous acid sterilizes 

 their flowers. The cornfields are sickly, patchy ; the brown-coloured 

 ears contain no grain. Haricots and cabbages are spotted white and 

 suffer much. The dead leaves of the potato shrivel and blacken. 

 The meadows remain sickly and turn brown. These sickly plants 

 have been analysed with great care by Morren, Stockhardt, Von 

 Schroder, Freytag, and Konig. They found that they all contained 

 an abnormal dose of sulphuric acid. It is important to insist on these 

 facts, so as to show the injurious action of sulphurous acid on plants. 

 Knowing this fact it is an easier task to contradict the opinion generally 

 held that sulphur acts on fungi by its conversion into sulphurous acid. 

 If it were so our vineyards, instead of becoming more vigorous by 

 sulphuring, would perish, since an infinitesimal quantity of acid 

 suffices to roast plants, and fructification, instead of being stimulated 

 as is the case, would be diminished. 



Action on Fungi. — -It follows from observations made on plants 

 that those which contain chloi-ophyll are more sensitive to the action 

 of sulphurous acid than those deprived of it. Sulphurous acid cannot 

 therefore be used to destroy fungi. 



Action on Insects. — To stifle insects the air must be saturated 

 with SO.,. Great care must therefore be taken in using this gas so as 

 to avoid its deadly action on plants. The great delicacy of the opera- 

 tion renders it less and less popular, hence the clochage of the vine 

 still in use in certain districts is gradually being replaced by scalding. 

 The phylloxera does not persist for twenty-four hours in an atmosphere 

 of this gas of 1 in 60 or 1 in 100. Mouillefert tested it in the soil 

 against phylloxera but without result. Moisture and the nature of 

 the soil destroy its toxic properties. 



Use in Diseases Treated by SOo in the Open Air. — Gum 

 Disease. — Swingle and Webber who examined the action of different 

 chemicals on this disease recommend to cure it, to clean the wounds 

 and coat them with an 18 per cent solution of SO^. 

 0! Anthonomus Piri, Boh., Anthonomiis Pomorum. — These formidable 

 destroyers may be removed in May by SO^, fumigations (Poupinel). 

 A dish of burning sulphur is moved about under the branches, or rags 

 dipped in molten sulphur and then lit. The trees should not be 

 fumigated with S0._, when in blossom, as the flowers would be sterilized 

 even if the contact was short and the acid in very small quantity. 

 Such fumigations also asphyxiate the grubs injurious to fruit trees, 

 who know how to shelter themselves from spraying in the common 

 nests which they spin. The most injurious are Hyponomeuta 

 Malinella, Zell. (small ermine moth) and Liparis chrysorrhaea (brown 

 tail moth). The grubs of these butterflies are only sensitive to fumes of 



