142 CYSTOPUS, OR WHITE RUST. 



been noticed by European observers. The only Continental 

 species that need be noticed are Cystopus Bliti and Cystopus 

 ForiiiiaccB. 



Cystopus Bliti (PL XVI., Figs. 25, 26). — In this species the 

 conidia are unequal, the terminal cell sterile, and smaller than the 

 rest ; membrane hyaline, somewhat ochraceous, often umbilicated ; 

 the other cells obovate or pyriform ; oospore globose, epispore 

 brown, surface reticulated. It is found on Amarautus Blitiim. 



Cystopus Portulace (PI. XVI., Figs. 27, 28) also has the 

 conidia unequal ; the terminal cell larger than the rest ; membrane 

 clear and yellowish, often umbilicated at the base, sterile or fertile. 

 Other fertile conidia yellowish, cylindrical. Oospores large, 

 globose ; epispore brown, covered with slightly raised, loose 

 reticulations. 



De Bary says this species inhabits both cultivated and wild 

 Purslane, but he had not observed it on any other plant. In the 

 garden where he observed it for several years in great abundance, 

 neither the Portulaca grandiflora nor P. lauceolata had the slight- 

 est trace of the fungus, though they grew quite mixed up with the 

 rusted Purslane. Cooke says this species should be watched for 

 in this country, for though the cultivation of Purslane is exceed- 

 ingly limited, the plant is remarkably liable to attack from this 

 parasite. 



The four British species are — Cystopus spimilosus, C. lepigoni^ 

 C. cubictis, and C. candidus. 



Cystopus spinulosus (PI. XVL, Fig. 29) has conidia, in time 

 much elongated; sori crumpent on both surfaces of the leaf, white; 

 oospores globose, epispore brown, tubercles minute, solid, very 

 prominent, often acute and spinulose. This species is sometimes 

 called the Thistle white rust, as it is found on thistles ; most 

 plentiful in September. 



Cystopus lepigoni. Sandwort White Rust. — Conidia unequal; 

 terminal cell sterile, globose ; membrane thickened ; fertile cells 

 sub-globose or cylindrical ; membrane hyaline ; oospores globose ; 

 epispore brown, tubercles minute, irregular, very convex, often 

 resembling spines. Found on Spergularia rubra from June to 

 September. 



Cystopus cubicus (PI. XVL, Figs. 22—24), Goat's-beard White 



