OBSERVATIONS ON THE VINE MILDEW. 285 



of extremely small insects. This explanation, however, not- 

 witlistanding the authority of Professor Fee, lias never appeared 

 to me completely satisfactory. Every one knows that when an 

 insect deposits one or more eggs under the epidermis, or in the 

 substance of vegetable tissues, a great activity arises in tlie 

 vegetation, and an unnatural development of the tisMies ; when, 

 on the contrary, they are deposited on the surface of the leaves, 

 their tissue is not affected, and they experience no change. 

 When an insect, then, has introduced an egg under the epi- 

 dermis, we ought to find the egg itself, the cavity in which it 

 is contained, and the modification of the tissues which it has 

 caused. But neither eggs nor cavities are ever observed, and 

 the epidermis alone is modified. It is very true that we find 

 amongst the threads of old patches of Erineum larvae and their 

 remains, as also mites and plant-lice. But if we examine the 

 upper surface of the leaf, we find no aperture pierced by the 

 insect in order to escape and live in a state of liberty ; the fila- 

 ments do not present the least solution of continuity in their 

 whole length ; their base always rests on the tissue of the 

 leaves, their free extremity is always obtuse and imperforate, 

 and their cavity does not inclose any traces of old skins or excre- 

 mential substances. Nothing then justifies the notion that 

 Erinea are, like galls, bedeguars, &c., the cradles of insects. If 

 indeed we meet by chance with insects or larvae, the species are 

 not so constantly the same as to justify us in referring to them 

 these accidental forms of vegetation. These observations do not 

 rest merely on the vine Erineum, but have been repeated on 

 those of the maple, the sycamore, the lime, and the birch. 

 Whether it resemble a tube or a flask, the accidental produc- 

 tion differs simply in form ; the organization and mode of deve- 

 lopment are the same. 



Though the vine Erineum, cannot then be attributed to the 

 pimcture of an insect with the view of depositing its eggs, may 

 we conclude that it is due to tlie puncture of the same insect 

 made in the leaves for the purpose of deriving nourishment 

 from them ? Certainly not. Every one knows that among'st 

 insects it is the Hemipterce which have the slenderest mouths. 

 But whether they live on animals or vegetables, they do not 

 derange or tear the tissues in the act of suction by means of the 

 different parts of which their nioutli is composed ; they employ 

 the most delicate acupuncture which it is possible to conceive ; 

 and as soon as the proboscis is introduced the juices ascend 

 simply in obedience to the laws of capillary attraction. May 

 •we suppose, however, tliat at the same time they introduce some 

 irritating fluid ? Nothing authorises this supposition ; and 

 besides, were it the case, what would be the condition of the 



