PREVENTIVE AND COMBATIVE MEASURES. 81 



the beech is omitted, and in the more elevated parts spruce 

 alone is planted. The fir alone is attacked by Plumia ahictina 

 Accidium datininn, Loi)hodcrmiu.m nervisequium, Trichosphaeria 

 pdvasitica ; the spruce, on the other hand, has to itself 

 Lophodermium macrosporum, Chrysomyxa ahietis, Hcrpotrichia 

 nirjra, while both are subject in youth to Pcstalozzia Hartviii, 

 and later to several wood-destroying fungi. 



The storing together of crops like apples, potatoes, onions, 

 turnips, etc., should be carefully carried out. They should be 

 handled as little as possible, and decaying individuals should be 

 sought out, and destroyed when possible, to save the remainder. 



IV. Selection of hardy varieties. 



An important method for the protection of plants from disease, 

 both from the preventive and remedial side, consists in the 

 selection and cultivation of varieties and species of plants able 

 to resist the attacks of parasitic fungi. 



It has already been mentioned that different varieties and 

 species show different powers of resistance against enemies. As 

 a further example, we have numerous American grape-vines 

 which are not attacked by downy mildew {Plasmop)ara viticola), 

 that dangerous enemy of the European vine of cultivation 

 ( Vitis vinifcra). Some American vines {cjj. Viiis riparia) 

 are proof against the phylloxera, the root-louse which attacks 

 the roots of European vines and devastates the vineyards of 

 the wine-producing countries ; while, on the other hand, othei- 

 American vines are no more resistant than the European. In 

 fact, it was the importation of those vines into Europe for 

 experimental cultivation which brought us both pliylloxera and 

 the downy mildew. The cultivation of sucli disease-proof 

 species would ensure us immunity from the phylloxera, if it 

 were not that the wine from these vines has neither the quality 

 nor the fiavour possessed by the European. On this account 

 tlie grafting of European vines on American stocks has been 

 introduced, whereby the roots remain unattacked by the 

 phylloxera, and the grapes are of the approved standard. Very 

 good results have also been obtained from experiments in 

 hybridization of American and European vines with the object 

 of obtaining roots from the American parent, and grapes from 



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