OBSERVATIONS ON THE VINE MILDEW. 293 



the vine on plants of Chrysanthemum Indicum placed purposely 

 beneath, and which were in consequence niateriallj'^ injured. I do 

 not for a moment doubt the correctness of a single observation of 

 Dr. Leveille, as far as it goes ; but the circumstances under 

 which disease of all kinds is propagated are so extremely variable, 

 that it is impossible to come to any conclusions from the simple 

 fact of certain individuals escaping wliere others are attacked, 

 and it is very easy to conceive that where the attack proceeded 

 from within the tissues, as in this case, if I am correct in my ob- 

 servations, the injury would be greater than where the fungus 

 was propagated secondarily on external surfaces from fallen 

 spores. It is very possible, that while superficial it may do no 

 further harm than clogging up the superficial spores, and hindering 

 the due access of light and air, and that it is only directly de- 

 structive where it enters the tissue through the stomata ; but 

 this, of course, is mere conjecture. The great point is to attend 

 to facts. The disease was observed in England about two years 

 previously to 1847, and till Mr. Tucker, after whom the mould 

 was named, employed the same remedy, or at least a form of it, 

 which has long been eflficacious in the case of peach mildew, the 

 destruction was complete. Mr. John Boys, an eminent solicitor 

 and magistrate at IMargate, who has long paid especial attention 

 to tlie cultivation of the vine, has informed me that one of his 

 own vines, and another which he had an opportunity of examin- 

 ing, were completely killed by it, and that in his case even the 

 pith of the branches was affected. He has told me besides, that 

 thirty plants of tlie Constantia grape, raised from eyes received 

 directly from tlie Cape, were all strongly affected, though there 

 was not tlie slightest reason to believe tliat the plants from which 

 the eyes were taken were diseased. Though the destruction was 

 at first complete as regarded the crojj, and, as stated above, in 

 two instances the disease was fatal to the vines themselves, since 

 he has adopted the system of washing the flues when warm, but 

 not too hot, with black sulphur and quicklime, in the proportion 

 of four ounces of each to sufficient rain-water to make the mix- 

 ture of the consistence of cream, with frequent syringing with 

 pure water, though the disease lias shown itself again and again, 

 his crop has not suffered.* In this case there was no question of 



* It is obvious that great caution must be exercised in this kind of fumi- 

 gation, and that a gentle current of air should be allowed to run from the 

 bottom to the top of the house (not, however, suffering the temperature to 

 get at first below 65°), as soon as the fumes have been allowed sufficient 

 time, which should never exceed an hour, even in the most virulent cases. 

 Indeed, under any mode of treatment, thorough ventilation is a most im- 

 portant element. The mixture of lime and black sulphur was used where 

 the flues were not of iron ; in the case of iron flues, it is recommended 

 simply to dredge them with sulphur : the heat, however, must not be such 

 as to ignite the sulphur. 



