SUBMERSION OF VINEYAEDS. 29 



the addition of nitrogenous manures. In spite of the good results 

 obtained by submersion and underground irrigation, these can only 

 be regarded as a palliative and not as a curative method. Long 

 winter submersions, short summer irrigations, do not kill all the 

 phylloxeras which ravage the roots, and a new invasion always occurs ; 

 thus the treatment should be annual. To diminish the number of 

 the insects and stimulate the vegetative energy of the plant is not a 

 sufficient remedy, and to re-establish the health of the plant it is well 

 to destroy the parasites by pow^erful insecticides, such as carbon di- 

 sulphide and sulphocarbonates, at the same time as the radicular 

 system of the vine is strengthened by subterranean irrigations. Simple 

 submersion along with strong manuring, by stimulating grow^th by 

 moisture and fertilizers perceptibly diminishes the action of the phyl- 

 loxera ; but it only creates, in reality, a modus vivendi between the 

 parasite and the plant. In these conditions the latter may produce 

 abundant growth of leaf, but it will only give in the majoiity of cases a 

 mediocre grape. It follows from the interesting researches of Maquenne 

 and Deherain, that when a soil is withdrawn from the action of 

 oxygen, as happens when it is covered by a sheet of water, the nitrates 

 which it contains disappear rapidly, owing to the action of certain 

 reducing ferments. On the other hand, Muntz has tried to find out 

 how the roots of vines immersed for two months can respire. This 

 long privation of air ought to be injurious. To prove it, Deherain 

 and Vesque submitted vines for fifteen days to immersion in. distilled 

 water, and found that they rapidly died, whilst others placed in 

 aerated water were in perfect health. It is, therefore, the want of 

 oxygen which in submersion may well prove fatal to vines, and that 

 more readily when it is practised during the period of activity of the 

 sap. Eiver water used for submersion is the best, because it always 

 contains air and nitrates, and vines submerged in these conditions 

 resist for two months at least. That is an established fact which it 

 is interesting to explain. The above-named scientific observers 

 believe that the nitrates reduced by the ferments are converted into 

 laughing gas which contains oxygen, and may support the respiration 

 of the roots. This reduction observed in submerged land may become 

 useful to vegetation, as it prevents the asphyxia of the vine. It is 

 thus necessary to spread on the land an appreciable amount of 

 nitrate if it be desired that the submersion should not injure the vine. 

 French vine growers use in fact 600 kilogrammes of nitrate per hectare 

 (528 lb. per acre), which is in no way exaggerated, but appreciably 

 increases the cost of immersion. Certain muddy waters, such as 

 those of the Dordogne and Garonne, for example, enable the amount 

 of manure to be reduced a little. How^ever, in spite of all the care 

 brought to bear on immersion, there are vines which do not support 

 the treatment. Espitalier cites the following species which die very 

 rapidly : La Carignac, le Grenache, le Mourvedre, la Clairette, le 

 Malbec, le Merlot, and in general all the valuable species, whilst the 

 Cabernet, the Petit Bouschet, and I'Aramon accommodate themselves 

 well to it. This explains why simple immersion has been replaced in 

 large vine-growing countries like the Gironde by irrigations with 



