320 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



other plants as well as the Vine. In days when it was regarded as a 

 complete or perfect fungus, it was called Botrytis cinerea, and that name 

 is found to he sometimes convenient now. 



The conidia form appears in tufts of a greyish colour, sometimes in 

 large patches. The stems or threads are stout, erect, dingy-olive, some- 

 what branched in the upper portion, the tip of each branch bearing a 

 somewhat globose tuft or cluster of broadly elliptical conidia (8-9 x 6 /u). 



The mycelium of the mould traversing the tissues of the host becomes 

 compacted into numerous small black sclerotia, which pass a period of 

 rest and afterwards produce again the conidial fruit, or the cuplike form. 



The little fleshy cups, or Sclerotinia, resemble a very miniature wine- 

 glass, with a long slender stem, the cups not more than one tenth of an 

 inch across, but the stem possibly more than half an inch long. The 

 inner membrane of the cup consists of cylindrical asci, or cells, packed 

 closely side by side, each containing right sporidia, which are the perfect 

 fruit. The sporidia are elliptical, colourless (10-11 x 6-7 /x). 



Spraying with dilute Bordeaux mixture destroys the conidia. Leaves 

 and other debris likely to contain the sclerotia should be collected and 

 burnt. 



Saec. Syll. viii. 799 ; Mass. PL Bis. p. 148, fig. 31 ; Thihn. Pilz. 

 Wcin. pp. 195, 197 ; McAlpine, Dep. Agri. Vict. p. 29. 



American Downy Mildew t . 

 Plasmopara viticola (B. & C), PI. XIII. fig. 10. 



The American mildew is not of the same character as the English 

 Vine mildew, inasmuch as whilst the latter is a surface mould in the 

 first instance, the former is an innate rot-mould, like the potato and 

 onion diseases. Not only is it North American in its origin, but it has 

 already found its way over to Europe and into the British Isles. 



This mould attacks all the green parts of the Vine. The mycelium 

 traverses the tissue of the leaves before there is any external manifesta- 

 tion. In time erect threads arise from this mycelium and find their way 

 in tufts through the stomata into the external air, and produce conidia. 



From five to eight of these fertile threads will issue through a breath - 

 ing pore, and form a tuft of white mould. Hence the under surface of 

 the leaves soon exhibits downy patches of the mould, and it came to be 

 called u downy mildew." The upper portion of the threads is branched 

 in a peculiar manner, and the conidia are borne on little points at the 

 tips of the branches. The primary branches alternate ; the secondary 

 br.mchos three- to four-furcate, the ultimate branchlets pointed, straight, 

 mort, usually four, bearing the ovoid conidia (from 8 x 12 /< to 

 7 x 80 h ). 



In time the conidia evolve from their contents five or six active 

 EOOBpores, armed with two cilia, by means of which they move about. 



Tn ' "tin r mode of reproduction is by resting-spores, which are sub- 

 globose (:;() :>,r> fl diam.), with a brownish smooth or slightly wrinkled 



coat. 



I! 1 mo elVectual remedy yet devised is spraying the Vines with a 

 I lution of sulphate of copper and lime. 



