FUNGOID PESTS OF CULTIVATED PLANTS. 159 



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 ju). 



Spraying with dilute Bordeaux mixture destroys the conidia. Leaves 

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

 burnt. 



Sacc. SylL viii. 799 ; Mass. PL Dis. p. 148, fig. 31 ; Thiim. Pilz. 

 Wein. pp. 195, 197 ; McAlpine, Dep. Agri. Viet. p. 29 ; Gard. Chron. 

 Jan. 20, 1906, p. 42. 



AMEBICAN DOWNY MILDEW, 

 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 " 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 

 branches three- to four-furcate, the ultimate branchlets pointed, straight, 

 short, usually four, bearing the ovoid conidia (from 8 x 12 fj. to 

 7 x 30 /u). 



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

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



The other mode of reproduction is by resting-spores, which are sub- 

 globose (30-35 ^ diam.), with a brownish smooth or slightly wrinkled 

 coat. 



The most effectual remedy yet devised is spraying the vines with a 

 solution of sulphate of copper and lime. 



Tubeuf, Dis. p. 128 ; Sacc. SylL vii. 806 ; Mass. PL Dis. 69, fig. 9, 

 p. 354; Gard. Chron. January 2, 1894, July 21, 1894; Farlow, Bull. 

 Buss. Inst. 1876, p. 415 ; Journ. B.H.S. 1878, p. 73 ; Thiim. Pilz. Wein. 

 p. 166 t. 1, f. 5. 



VINE BOOT CLUBBING. 

 Plasmodiophora Vitis, PI. XIV. fig. 12. 



One of the latest importations of vine diseases is that known as 

 " vine clubbing," which does not differ greatly from the clubbing in 



