284 OBSERVATIONS ON THE VINE MILDEW. 



XXVIII. — Observations on the Vine Mildeio. By J. H. 

 Leveille, D.M.* Translated from the French, with Remarks 

 by the Rev. M. J. Berkeley, M.A , F.L.S. 



" The gardeners in the neighbourhood of Paris have, unhapjuly, 

 too much reason for remembering the damage done to their 

 grapes last year by the Oidium Tuckeri. Under these painful 

 impressions they are at this very time watching their trellises 

 every instant, and tui'ning up the leaves in seai'ch of the baneful 

 mould. Some return from their observations satisfied witli the 

 result, but otiiers alarmed, because they have discovered certain 

 spots on the lower surface of the leaves, which they believe to 

 be clearly due to its presence. 



It is, I think, useful to destroy this false notion, which is so 

 generally diffused, and which is causing so much anxiety. What 

 is at this moment taken for Oidium Tuckeri, the mould which 

 destroys the grapes, is merely the Erineum of tlie vine, wliich has 

 always existed, and which has never attracted much attention, 

 because it is not, in point of fact, injurious. 



To avoid this mistake it will suffice to call to mind that the 

 vine Erineum is constantly produced on the lower surface of 

 the leaves, where it forms spots varying in number and extent. 

 It forms a lining to the depressions, which are the counterpart 

 of the blisters which render the upper surface unequal and tuber- 

 culated. As soon as it begins to be developed the surface 

 purses up and exhibits a manifest change of colour. It is at 

 first white, rose-coloured, or pale violet ; then it assumes a tawny 

 or rusty tint ; even with the naked eye it is clearly due to an 

 anomalous development of the hairs, which assume the appearance 

 of threads. To understand their nature perfectly it is necessary 

 to have recourse to the microscope, under which they appear to 

 be elongated, Jiollow, cylindrical tul)es, without any partitions 

 through their whole length, and absolutely empty. The mem- 

 brane of which they are composed is simple, uniform, witliout 

 reticulations, and of the same nature with tlie epidermis, of wliich 

 it is a continuation. This fact is beyond all doubt, only tlie true 

 cuticle forms no part of them, because it has been destroyed or 

 perforated by the development of the subjacent cells. This at 

 least seems to be indicated by a liti le circular line, or a slight 

 irregularity which exists at the base of each of the tlireads of 

 which the Erineum is composed. 



The causes of this anomalous growth of the hairs are entirely 

 unknown. It is regarded generally as the result of the puncture 



* Recherches sur la Maladie des Vignes, par J. H. Leveille, D.M. 

 Extrait de la Revue Horticole, No. du 18 Juin, 1851. 



