318 .JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The mould, like other species of Oidium, has a creeping mycelium, which 

 supports erect fertile threads, and these latter become differentiated into 

 chains of colourless spores or conidia. 



Some writers are of opinion that this disease is the same as the 

 " powdery mildew " of the United States, the full development of which is 

 known under the name of Uncinula spiralis ; but as the receptacles, or the 

 Erysiphe condition, have never been found in Europe, it is still a doubtful 

 point. It is more than probable that the Oidium Tuckeri, as known to 

 us, is an imperfect fungus of which the full development would naturally 

 be a very close associate of Uncinula spiralis, if not really the same 

 species. 



As an epiphyte, the application of sulphur has been the only success- 

 ful remedy, or sulphur in combination with lime. 



Gard. Chron. May 15, 1886 ; 1847, p. 779 ; 1878, p. 74. Joum. B.H.S. 

 1878, p. 68. Thiim. Pilz. Wein. p. 1, t. 3, f. 1. 



Powdery Mildew of Vine. 

 •"« Uncinula spiralis (B. & C), PI. XIV. fig. 13. 



American botanists are generally satisfied that this Vine disease of 

 theirs is a fruitful development of the English Vine disease, which we 

 only 'know, in the conidial form, as Oidium Tuckeri, for which reason, 

 therefore, it is entitled to some notice here. 



It forms white or greyish patches on the surface of the leaves, young 

 shoots, and fruit. This is composed of the interwoven threads of the 

 mycelium, from which afterwards arise short erect branches, the upper 

 portion of which becomes converted into a chain of conidia, the final one, 

 which is the oldest, falling away when mature, giving to the white patches 

 a still more powdery appearance. 



Towards the end of the summer, the globose conceptacles make their 

 appearance amongst the mycelium, at first yellow, afterwards dark brown, 

 attached at the base by delicate threads. Encircling the base, a series of 

 Bpreading, straight, simple appendages radiate around the conceptacles, in 

 number from ten to twenty, the tips of which are hooked or spirally 

 twisted, and the lower part, next the conceptacles, coloured. The asci or 

 sacs, within the conceptacles, enclose from four to six elliptical sporidia 

 (20x8-10//). 



Jowrn. R.H.S. 1878, p. 68 ; Thiim. Pilz. Wein. p. 183; Grevillea, iv. 

 159 ; Gard. Chron. 1878, p. 74 ; Mass. PI. Dis. pp. 93, 360, fig. 14; 

 Tnhevf, Dis. p. 176. 



In the United States another species of the same genus (Uncinula 

 subfusca) attacks the living leaves of Vitis Labrusca. 



Australian Vine Mildew. 



Erysiphe vitigera (C. & M.) 



This i tli, Yme mildew which in Australia corresponds to the powdery 

 mildew <>f the United States, and to our own Oidium Tuckeri. In its early 

 manifestations, and the conidial stage, it might be taken for Oidium 



