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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



enemies. One or more of these may at any time make their appearance 

 in the garden, especially those in which Clematis Vitalba may have 

 secured a place. Hence we enumerate, incidentally, the diseases to which 

 the Clematis is liable. 



The common Clematis cluster cup (JEcidiwm Clematidis) occurs over 

 the greater part of Europe, on the leaves of C. Vitalba, C. recta, and C. 

 Flammula. 



Another cluster cup {JEcidium Engleriaimm) has been found on 

 Clematis leaves in Abyssinia. 



In India another species (JEcidium orbiculare) has been found on C. 

 grata, C. orientalis, and C. puberuXa, whilst JEcidium Otagense is confined 

 to New Zealand. 



Leaf -spot is also common, with Phyllosticta Vitalba (Cooke), formerly 

 included by error under Septoria Clematidis, on our indigenous species. 

 Phyllosticta Clematidis in Canada ; Phyllosticta corrodens upon Clematis 

 Vitalba in Italy, in company with Phyllosticta bactcriosperma. 



One form of leaf-spot, with bicellular conidia, is Ascochyta Vitalba, 

 found in France. 



Of leaf-spots having long threadlike conidia Septoria Clematidis is 

 British, as well as proper to some other parts of Europe. Septoria 

 clematis — Flammula, on C. Flammula in France ; Septoria clematis-recta 

 on C. recta in Italy, as well as Septoria Flammula on C. Flammula, and 

 Septoria Viticella on C. Viticella. To these may be added Septoria 

 Jcnissensis on C. glauca in Siberia, and Septoria Jachnanni on C. Jach- 

 manni in New York. 



Crucifer Rot-mould. 

 Perouospor a parasitica (Pers.), PI. VI. fig. 30. 



There are but few parasites on garden Crucifers, but this is sufficiently 

 destructive to the foliage of Wallflowers, Stock, and some other garden 

 flowers to make up for the deficiency. 



It occurs in whitish mouldy patches on the leaves and inflorescence. 



The mycelium is profuse, thick, and very much branched, from which 

 arise the erect threads, which are also rather thick, soft, and flexile, from 

 five to eight times branched, in a forked or trifurcate manner, the ultimate 

 branches awl- shaped and curved, bearing the broadly ellipsoid conidia 

 (20 22 x 10 20 



The resting spores, which are seated upon the mycelium in the stems 

 and branches of the host, are globose (26-40 ^ diam.), either smooth or 

 rugged, and of a yellowish or tawny colour. 



For details of life history and development of the rot-moulds see 

 Introduction, p. 2. 



Diseased parts should be burnt to destroy resting spores. 



8ace. SfU. vii. 880; Cooke M. F. t. 14, f. 205 ; Hdbk. No. 1778; 

 Mats. PL Dis. 79, 855 ; Mass. P. F. 119, f. 45, 46, 120. 



Poppy Rot-mould. 

 Peronospora arborescens (Berk.), PI. VI. fig. 15. 

 This is the principal pest of the Poppy family, and occurs on the 

 leaves of the Opium Poppy, as well as on those of some uncultivated 



