60 FUNGOID PESTS OF CULTIVATED PLANTS. 



Convolvulus Anthracnose. 

 Marsonia Ipomcea (C. & M.), PL IV. fig. 73. 



The cultivated species of Convolvulus and Ipomoea do not appear to 

 be susceptible to fungus parasites in this country, although some half- 

 dozen species are recognised abroad. 



The above-named was first discovered on the stems of Ipomcea in 1887, 

 and occasionally on the leaves. The pustules were densely collected on 

 the stems of living plants, elevating and splitting the cuticle in an 

 irregular manner, then becoming dark-coloured, like the pustules of a 



Credo. 



The conidia, or sporules, ooze out in tendrils, especially when moist, 

 and are narrowly oblong or cylindrical, blunt at the ends, and divided in 

 the middle by a transverse septum (10-15 x 3 /i), entirely colourless. 

 At first the conidia are produced upon short spore-bearers, which proceed 

 from a cushion-like base, but they soon break away, and form a gelatinous 

 mass. 



The majority of the species of Glceosporium and Marsonia are very 

 destructive and persistent pests, against which fungicides have proved of 

 little avail. Destruction of infected plants seems to be the only safe 

 remedy. 



Sacc. Syll. x. 6900 ; Grevillea, xvi. 48. 



Kivea Chain Mould. 

 Oidium ericmpens (C. & M.), PI. IV. fig. 74. 



It was in the autumn of 1887 that the leaves of Rivea hypocrateri- 

 formis, under cultivation, were found to develop, on the under surface, 

 little tufts of a whitish mould, which soon gave a sickly complexion to 

 the foliage. The tufts, which broke through the cuticle, were rounded 

 and convex, of a greyish colour, becoming darker with age. 



The threads composing the tufts were rather robust, and divided in 

 the upper portion, which soon became torulose, or beadlike, and then the 

 cells separated as globose conidia, or nearly globose (7x5 p), and 

 became sprinkled over the leaf. 



This mould is more tufted and less diffuse than in most species of 

 Old in in, but the structure is the same. 



NO opportunity occurred for experiment, but it is possible that an 

 application of sulphur would be the most effective. 



There is no record of this species anywhere other than in Great 

 Britain. 



Sacc. Syll. x. 7091 ; Grevillea, xvi. 49. 



Numerous parasites are recorded in North America as attacking the 

 different Bpecies of Phlox, but hitherto none have given any trouble in 

 this country. 



Henbane Rot-mould. 

 Pcronospora Hyoscyami (De Bary), PL VI. fig. 78. 

 This pest has assumed additional importance since it has made 

 vigorous attacks upon Tobacco plants under cultivation, both in North 

 America and Australia. 



