VINE MILDEW. 121 



considered as producing only naked spores. A German botanist 

 {Bot. Zeit., 1853, p. 134), who has either not read or forgotten 

 my observation, has, after a lapse of four years, published this 

 fact as new, though professedly passing in review all the writers 

 who have spoken of Eurotium. The Annales des Sciences 

 Naturelles is not, however, a publication of such obscurity as 

 may justify a writer who has not consulted it. Some doubtless 

 would have taken occasion to propose a new genus. We may 

 therefore at least be thankful to him so far for his reserve. 



A new question now arises ; is Oidium or Erysipbe Tuckeri, 

 by whichever name it may be known, really an autonomous species 

 and distinct from its allied congeners, and especially from 

 O. Erysiphoides, to which it comes the nearest ; or is it merely a 

 form or variety '? The peculiar habitat which it has chosen, from 

 which it has not migrated to surrounding plants, the observation 

 of Molil in his first memoir of an infected vine which did not 

 communicate the disease to Ampelopsis quinquefolia, which was 

 intertwined with it, and finally the fruitless attempts of Mohl and 

 others to propagate it on other plants, lead to the belief that it is 

 not a modification of some species already known, but a legitimate 

 species in the sense applied to this word by botanists. But it 

 may be asked, where was the Oidium before it attacked the vines ? 

 Is it a spontaneous production ? To such questions I can only 

 answer with Montaigne — Que sais-je ? 



As regards the first development of the parasite, or rather its 

 invasion in spring, the opinion of Mohl, whom T quote in preference 

 because he appears to have observed accurately, is that it first 

 shows itself on the lowest internode of the new shoot. " On the 

 branches the parasite occurs regularly on the lowest and oldest 

 internodes ; large spots covered with the fungus appear on these, 

 and at a later period on the intermediate internodes, while the 

 upper internodes (as is at present universally the case here) are 

 altogetlier free. The fungus often spreads to the ovaries from the 

 peduncles, which are already attacked before the blossoms expand, 

 since the threads of the mycelium, a short time after the corolla 

 falls, creep over the nectary and involve the berries, commencing 

 at their base." I cannot quit this vexatious parasite without 

 speaking of some experiments of which it has been the subject, and 

 which have given occasion to certain strange and, as I believe, 

 erroneous assertions. A botanist, known for many excellent 

 works on other matters of Botany, has been induced by observation 

 of the artificial germination of the acrogenous spores of the 



