WHITE RUST OF CRUCIFERS 61 



The 'Kerguelen's Land Cabbage' (Pringlea antiscor- 

 buticci}, although exempt from the disease in its native 

 land, could not be kept in cultivation at Kew, owing to 

 the attacks of this parasite. 



Among economic plants attacked may be mentioned 

 horse-radish, cabbage, radish, cress, wall-flower. The caper 

 plant (Capparis spinosa) also suffers. 



PREVENTIVE MEANS. Infection only takes place during 

 the seedling stage, hence the disease does not spread 

 among older plants. 



Diseased plants, both wild and cultivated, should be 

 destroyed. 



De Bary, Ann. Sci. Nat. (Sot.}, ser. iv., vol. 20. 

 Prillieux, Malad. des Plantes Agric., i. p. 62, figs. 

 Wager, Ann. Bot.^ vol. x. p. 89. 



Cystopus tragopogonis, Schrot. = Cystopus cubicus, De 

 Bary. This fungus forms white blisters on various umbel- 

 liferous plants, goat's-beard (Tragopogori), scorzonera, 

 salsify, etc., frequently attacking all the plants in a bed, 

 and doing considerable injury. In this species the ter- 

 minal conidium of a chain differs in structure from the 

 remainder in having the wall thick throughout, whereas 

 the others have a thin wall with an equatorial thickened 

 band. The oospore has the epispore or outer wall densely 

 covered with minute warts or papillae, whereas the same 

 structure in Cystopus candidus is ornamented with large, 

 irregularly-shaped warts. 



