FUNGOID PESTS OF CULTIVATED PLANTS. 27 



Sacc. Syll. vii. 2174 ; Cooke Hdbk. No. 1626 ; Gard. Chron. 1876, 

 175, 861, fig. 72 ; Cooke M. F. 198 ; Grove Journ. Bot. 1883, p. 274 ; 

 Plowr. Brit. Ured. 158. 



VIOLET ROT-MOULD. 

 Peronospora Viol (D. Bary), PL VI. fig. 24. 



Amid all the vicissitudes of the Violet crop it has hitherto suffered 

 little serious injury from the rot-mould, which is of close kindred to the 

 Potato disease mould. It has appeared, and is not uncommon, on wild 

 plants, and has recently invaded the Violet and Pansy under cultivation. 



The tufts of the mould are effused on the foliage, and although white 

 are not particularly conspicuous ; the threads are collected in little bundles, 

 growing erect, and are many times divided in the upper portion into 

 forked branches, with the final branchlets awl- shaped and bent backwards. 



The conidia are elliptical, growing singly at (22-27 x 15-19 /z) the tips 

 of the branchlets, but with a slight tinge of violet in their colour. 



It is assumed that resting spores are produced, as in other rot-moulds, 

 but they have not yet been detected. (See Introduction, p. 3.) 



Plenty of air, and not too much water, retard the spread of the disease. 



Another rot-mould (Peronospora megasperma) has been found on 

 Viola tricolor in the United States. 



Sacc. Syll. vii. 838 ; Berlese Icones, t. xlii. ; Mass. PL Dis. 80 ; 

 Cooke M. F. 235 ; Grevillea, iv. 109 ; Mass. B. F. p. 121. 



VIOLET WHITE MOULD. 

 Bamularia lactea (Desm.), PL I. fig. 23. 



This common little white mould on Violet and Pansy leaves does not 

 much trouble the cultivator, since it has preference for the wild plants. 



White orbicular spots appear on the leaves, circumscribed by a brown 

 line, three or four spots being usually present on one leaf. The mould 

 gives a mealy appearance to the spots, as if they had been powdered with 

 flour, and principally on the under surface. 



The mould itself is a very simple structure, consisting of rather 

 twisted short threads (30-60 /* long), without branches, bearing at their 

 tips the oblong or spindle-shaped conidia (8-10x2-3 p). Occasionally 

 two or three of the conidia will be met with attached to each other, end 

 to end, so as to form a short chain. 



It has been suspected that many of the species of this genus of moulds 

 are only the naked conidia of some higher form of fungus, as has been 

 proved in a few cases. 



The present mould is known, not only in Britain, but also in France, 

 Germany, Bohemia, Austria, and Italy. 



It seems to be amenable to fungicides if taken in time. 



Sacc. Syll. iv. 979 ; Journ. Boy. Agr. Soc. Ixi. (1900), p. 735 (sub 

 Ovularia lactea); Journ. B.H.S. xxvi. (1901), p. 198; Grevillea, iv. 

 p. 109. 



Another species, Eamularia agrestis, with larger and sometimes 

 septate conidia, has occurred on Violet and Pansy leaves in Italy. 



