156 FUNGOID PESTS OF CULTIVATED PLANTS. 



Vine Leaf-tuft Mould. 

 Isariopsis clavispora (B, & C), PI. XIII. fig. 7. 



This appears to be entirely an American species, but authors have 

 confounded it with Cercospora viticola, and may do so again. We are not 

 aware that it has been found on any other living leaves than those of 

 Vitis Labrusca, and was first described by Berkeley. 



The spots are brown, and mostly irregular. The compacted hypha 

 are closely united in the lower portion, but become loosened and flexuous 

 near the apex. The conidia are narrowly clavate, round at the apex, and 

 multiseptate (as many as 7-9), hyaline and attenuated downwards, but 

 brownish above (100 x 5-6 /a), each cell sometimes including a small 

 guttule. 



Careful examination will convince anyone that the conidia are attached 

 by the thin extremity, and that they can hardly be regarded as a topsy 

 turvy condition of Cercospora viticola. 



Sacc. Syll. iv. 2998 ; Berk. & Curt., Grcvillea, iii. p. 100, No. 619 ; 

 Thiim. Pilz. Weill. 177, t. 5, f. 7 (bad). 



Other black moulds, of which many have been named in connection 

 with the Vine, appear to be saprophytes, with the exception, perhaps, of 

 Fumago vagans, which has a wide range of hosts, and may soon be dis- 

 posed of, if it ventures to appear in a well-ordered vinery. 



English Vine Disease. 

 Oidium Tuckeri (Berk.), PI. XIII. fig. 8. 



The ordinary English Vine disease was first observed in 1845 at 

 Margate by a gardener, Edward Tucker, and it is known to this day as 

 Oidium Tuckeri. In 1853 it appeared in Spain, and a year later in 

 Portugal. It was first observed in Madeira in 1851, and was not long in 

 spreading through the continent of Europe. 



The disease is too well known to need description. When the shoots 

 are struck they become spotted with dark grey or rust colour ; the leaves 

 also become spotted, and covered with a cottony substance of fine fila- 

 ments, as seen under the microscope. The Grapes are covered with what 

 yppears to be a white powder, like lime, a little darkened with brown. 

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

 supports erect fertile tbu-eads, 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. 



