300 CHAPTERS ON FUNGI. {October, 



distinct species of all these parasites, which should rather be con- 

 sidered as varieties of a few principal forms. 



I shall take examples from the genera j^cidium and Uredo. 



^CIDIUM. 



Spores free, contained in a cellular, membranous sac (pseudo- 

 j)eridium) , distinct from the epidermis, and at length bursting at 

 the apex. 



tEcidium Berberidis, Pers. Berberry jEcidium. Spots round- 

 ish, bright red ; subiculum (thickened part of the leaf) rather 

 thick ; pseudoperidia disposed in subrotund or oval patches, often 

 greatly elongated; spores orange. — Grev. Sc. Crypt. Fl. t. 97. 



On the leaves, peduncles, and sometimes even on the flowers 

 and fruit of the common Berberry. 



A common and pretty parasite. The spots on the upper side 

 of the leaves are of a bright red, and the clusters of pseudoperidia 

 which are produced on the under side, are of a fine orange-colour. 

 The pseudoperidia themselves are pale-orange, and cylindrical in 

 form, with the orifice somewhat reflexed and dentate. The con- 

 tained globular spores are of a darker orange hue. 



Uredo. 



Spores free, aggregate, covered by the epidermis of living 

 plants. 



Uredo (Ustilago) segetum, Pers. Smut. Growing on the 

 receptacle and rachis ; epidermis soon ruptured ; spores loose, mi- 

 nute, spherical, black. 



On wheat, barley, oats, etc. Very common and destructive. 



The "black heads" to be seen everywhere among crops of 

 growing corn are caused by this Fungus, which soon destroys 

 the whole head, converting it into a black powdery mass, which 

 adheres to and stains everything that touches it. The spores, 

 which are very minute, are of a dark olive-colour, though appear- 

 ing black when viewed " en masse." 



Uredo Rubigo, DC. Rust. Spots yellow, heaps oval, scat- 

 tered, generally epigeous ; epidermis at length bursting longitu- 

 dinally ; spores subgiobose, red-brown, easily dispersed. 



On grasses and corn. Common. 



This, along with another species, U. linearis, is known under 

 the common name of " Rust," and often damages corn crops con- 



